Disc brake actuator

Abstract

The actuation device (1) for the disc brake (2) comprises a piston (7), a first ramp ball motion converter (100) having a first ramp portion (101) axially constrained and operable in rotation about an actuation axis (8), a second ramp portion (102) coupled to the piston (7), a plurality of rolling elements (29) interposed in contact with a ramp (103) formed by the first ramp portion (101) and the second ramp portion (102), a second screw-nut motion converter (4) connected between the second ramp portion (102) and the piston (7), and a torque limiter (10), which forms a torsional connection between the first ramp portion (101) and the second ramp portion (102) and causes them to rotate together about the actuation axis (8) until a predetermined limit torque in the torsional connection is reached, and when the predetermined limit torque is exceeded, disengages the rotation of the first ramp portion (101) relative to the second ramp portion (102) about the actuation axis (8).

Description

[Technical Field]

[0001] The present invention relates to an actuating device for a disc brake, in particular an actuating device for an electromechanical disc brake, and to a disc brake equipped with such an actuating device. [Background technology]

[0002] Actuator devices for disc brakes are known that include a gear motor associated with a ball screw and convert torque generated by the gear motor into a linear braking force directed to the disc brake pads.

[0003] The ball screw serves two functions in these actuators: first, to transfer the braking force to the disc brake pads so that the pads apply a braking torque to the disc brake; and second, to recover and compensate for pad wear.

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

[0005] Indeed, these actuators have a high axial dimension, ie in the direction of application of the braking force, high cost, noise and weight.

[0006] Another drawback of ball screw actuators is the impossibility of defining a nonlinear advance law. In fact, ball screws have a constant thread pitch and therefore a linear advance law that is directly proportional to the angle of rotation of the screw.

[0007] On the other hand, it would be desirable to have an actuator with a non-linear advance that better matches the distinct steps of closing the piston until piston-pad-disc contact is achieved and tightening the piston to clamp the pad against the brake disc.

[0008] Another known actuation device is the so-called "ball-in-ramp" mechanism. A ball-in-ramp mechanism is also a mechanism for converting rotational motion into translational motion and consists of two opposing components that can rotate relative to one another and a number of balls that are interposed in contact between the two opposing components and received in rolling tracks (or ramps) formed on the two components. The rolling tracks unfold in a spiral such that relative rotation between the two opposing components creates a wedge effect and their axial translation moves them away from each other.

[0009] Ball-in-ramp mechanisms have a much smaller axial dimension than ball screws and are capable of generating either very high linear or nonlinear braking forces depending on the relative rotation angle of the two opposing components (according to the conformation of the ball ramp).

[0010] However, known ball-in ramp mechanisms have the disadvantage that axial movement is very limited and it is difficult to recover wear on the disc brake pads. Summary of the Invention

[0011] SUMMARY OF THE INVENTION It is an object of the present invention to provide an actuating device for a disc brake having features which avoid at least some of the drawbacks of the prior art.

[0012] A particular object of the present invention is to provide an actuating device for a disc brake having small axial dimensions and low cost and weight, with the same or improved braking efficiency.

[0013] A more specific object of the present invention is to provide an actuator for a disc brake that can be configured with a non-linear advance law.

[0014] It is a further object of the present invention to reconcile the seemingly contradictory requirements of small axial dimensions, which are currently incompatible with the use of screw motion converters, and extra piston travel to recover pad wear, which are currently incompatible with the use of ramp ball designs.

[0015] These and other objects are achieved by an actuating device for a disc brake according to claim 1.

[0016] The dependent claims relate to preferred and advantageous embodiments of the invention. [Brief explanation of the drawings]

[0017] In order to better understand the invention and to appreciate its advantages, some non-limiting exemplary embodiments thereof will now be described with reference to the accompanying drawings, in which:

[0018] [Figure 1] FIG. 1 is a perspective view of a disc brake according to one embodiment of the present invention.

[0019] [Figure 2] FIG. 2 is a cross-sectional view taken along a radial plane of a detail of a disc brake according to an embodiment of the present invention.

[0020] [Figure 3] FIG. 3 is an exploded view of an actuation device for a disc brake according to an embodiment of the present invention.

[0021] [Figure 4A] FIG. 4A is a partially assembled perspective view of an actuation device for a disc brake according to an embodiment of the present invention.

[0022] [Figure 4B] FIG. 4B is an assembled perspective view of the disc brake actuator of FIG. 4A.

[0023] [Figure 5] FIG. 5 is a radial cross-sectional view of the actuator of FIG. 4B.

[0024] [Figure 5A] FIG. 5A is a particular view of an actuator, according to an embodiment of the present invention.

[0025] [Figure 5B] FIG. 5B is an exploded view of details of an actuator according to an alternative embodiment to that of FIG.

[0026] [Figure 6A] FIG. 6A is a cross-sectional view taken perpendicular to the actuation axis in a first operating configuration.

[0027] [Figure 6B] FIG. 6B is a cross-sectional view perpendicular to the actuation axis in the second operating configuration.

[0028] [Figure 7] FIG. 7 is a cross-sectional view taken along a radial plane of a detail of a disc brake according to a further embodiment of the invention.

[0029] [Figure 8] FIG. 8 is an exploded perspective view of an actuation device for a disc brake according to a further embodiment of the present invention.

[0030] [Figure 8A] FIG. 8A is a further exploded view of the actuation device for the disc brake shown in FIG.

[0031] [Figure 9] FIG. 9 is a perspective view of a partially assembled actuation device for a disc brake according to a further embodiment of the present invention.

[0032] [Figure 10] 10 is a radial cross-sectional view of the assembled actuator of FIG.

[0033] [Figure 10A] FIG. 10A is a radial cross-sectional view of an actuation device for a disc brake according to an embodiment of the present invention.

[0034] [Figure 11A] FIG. 11A is a partially assembled perspective view of an actuation device for a disc brake according to an embodiment of the present invention.

[0035] [Figure 11B] FIG. 11B is a perspective view of an assembled actuator for the disc brake of FIG. 11A.

[0036] [Figure 12] FIG. 12 is a radial cross-sectional view of an actuation device for a disc brake according to a further embodiment.

[0037] [Figure 13A] FIG. 13A is a perspective view of an actuator according to a further embodiment of the present invention.

[0038] [Figure 13B] FIG. 13B is a front view of the actuator in FIG. 13A. DETAILED DESCRIPTION OF THE INVENTION

[0039] In the following description, the term "forward" orientation refers to the orientation of a side, face, surface, etc. in the direction of piston advancement (braking) unless otherwise specified, and the term "rearward" orientation refers to the orientation of a side, face, surface, etc. in the direction of piston retraction. The terms "radial", "circumferential" and "axial" are intended to refer to the working axis of the piston unless otherwise specified.

[0040] Referring to the figure, an actuating device 1 for a disc brake 2 has the following configuration.

[0041] A piston 7 is supported slidably along an actuation shaft 8 .

[0042] First ramp ball motion converter 100. First ramp ball motion converter 100 has a first ramp portion 101 that is axially stationary and rotatable about actuation axis 8, a second ramp portion 102 that is coupled to the piston and faces first ramp portion 101, and a plurality of rolling elements (balls) 29 that are in contact with and interposed between a ramp 103 formed by first ramp portion 101 and second ramp portion 102. Thus, rotation of first ramp portion 101 relative to second ramp portion 102 results in braking movement of second ramp portion 102 together with piston 7 relative to first ramp portion 101 along actuation axis 8.

[0043] A second screw and nut motion converter 4 without ball recirculation. The second screw and nut motion converter 4 is connected between the second ramp 102 and the piston 7 such that rotation of the second ramp 102 relative to the piston 7 about the actuation axis 8 results in a further compensating translation of the piston 7 relative to the second ramp 102 along the actuation axis 8.

[0044] Torque limiter 10 (or in other words, torsion clutch). The torque limiter 10 is - forming a torsional connection between the first ramp portion 101 and the second ramp portion 102, and rotating the first ramp portion 101 and the second ramp portion 102 together around the operating shaft 8 until a predetermined limit torque is reached in the torsional connection; When the predetermined limit torque is exceeded, the rotation of the first ramp portion 101 relative to the second ramp portion 102 around the operating shaft 8 is cut off.

[0045] As a result, in the first step of moving the piston 7 closer to the pad until piston-pad brake disc engagement is achieved (the extra travel step required to compensate for worn pad thickness), both ramp portions 101, 102 of the first ramp ball motion converter 100 rotate together to advance the piston 7, under the action of the second screw-nut motion converter 4 only.

[0046] At the end of the first approach step, the piston pad disc brake pressing engagement increases the mechanical resistance to further advancement of the piston 7 until a predetermined limit torque is exceeded in the torsional connection between the first ramp portion 101 and the second ramp portion 102, and their relative rotation causes a braking translation of the piston 7 (for a very limited braking movement) only by the action of the first ramp ball motion converter 100.

[0047] The first ramp part 101 can be connected to an input shaft or a general input rotating element 3, for example a reduction gear or an electric motor.

[0048] Conventionally, the piston 7 is arranged to transmit an axial force in the direction of the actuation axis 8 onto the disc brake pads 9 of the disc brake 2 .

[0049] Advantageously, an actuator 1 configured in this way is more compact and lighter than prior art actuators.

[0050] Furthermore, the actuator 1 does not require the use of a ball screw and is small in size, lightweight, and low in cost.

[0051] Furthermore, the actuator 1 configured in this way harmonizes the requirements of braking travel with high force and good motion reversibility, high efficiency, and irreversible, low-force travel to compensate for wear of the pads 9.

[0052] The actuator 1 configured in this way converts torque from the rotating element 3 into linear force in two distinct operating steps. In the first step, the piston 7 is moved closer to the pads 9 of the disc brake 2 to restore wear on the pads 9. This operation is achieved by the second screw-nut motion converter 4 with a low force, i.e., a force lower than the braking force. The actual braking, i.e., the generation of a braking force by the piston 7 on the pads 9 of the disc brake 2, occurs in the second step. The translational motion of the piston 7 that generates the braking force is generated by the second ramp-ball motion converter 100.

[0053] Detailed Description of First Ramp Ball Motion Transducer 100

[0054] According to an embodiment of the present invention, the first ramp portion 101 may itself form the input rotation element 3 of the device 1, and the second ramp portion 102 may be formed directly on the screw body 5 of the second screw-nut motion converter 4.

[0055] This increases the compactness of the actuation device 1 and reduces its space requirements in the direction of the actuation axis 8 .

[0056] According to an advantageous embodiment, the first ramp portion 101 is formed by a substantially cylindrical rotor body 23 having a circumferential rotor wall 25 extending in the direction of the operating axis 8, a rotor front wall 26 and a rotor rear wall 27.

[0057] The rotor front wall 26 faces the forward direction of the piston 7 and forms one or more, preferably three, first rolling tracks 28 of the ramps 103, and also forms a drive shaft 24 that protrudes from the rotor front wall 26 coaxially with the operating shaft 8 and is connected to the torque limiter 10. The drive shaft 24 may further form a rotatable centering support for the second ramp portion 102.

[0058] The circumferential rotor wall 25 may form teeth 50 extending about the actuation axis 8, for example to the rotor rear wall 27, for transmitting actuation torque / rotation.

[0059] According to an alternative embodiment (FIG. 12), the rotor body 23 is formed as a radial enlargement of the shaft 48 which forms both the axially extending drive shaft 24 of the actuator 1 and the input shaft extending rearward of the rotor body 23 opposite the drive shaft 24.

[0060] According to an embodiment, the first motion converter 100 comprises a bearing assembly 105. The bearing assembly 105 is configured to rest the first ramp part 101, and in particular the rotor body 23, concentrically and translationally relative to the actuation axis 8 to support axial loads occurring during operation of the actuation device 1, and possibly also radial loads due to engagement with the teeth 50.

[0061] Advantageously, the bearing assembly 105 is located within the rotor body 23, coaxially therewith, possibly at the location of the teeth 50 (to provide a radial reaction constraint directly thereon).

[0062] The bearing assembly 105 may consist of a four-point contact rolling bearing.

[0063] According to an embodiment, the rear threaded wall 21 of the screw body 5 faces the rotor body 23 and forms at least one, preferably three, second rolling raceways 22 of the cam track 103 .

[0064] Advantageously, the first rolling raceway 28 and the second rolling raceway 22 facing each other each accommodate a rolling ball 29 therebetween.

[0065] The ramps 103 of the ramps 101, 102 extend helically (in other words, eccentrically in the circumferential direction) relative to the actuation shaft 8. Each of the ramps 101, 102 may form, for example, two or three rolling paths 103 arranged consecutively in the circumferential direction and separated from one another by separating ribs, to accommodate the rolling elements (balls) 29 at predetermined positions.

[0066] The ramp 103 is configured as a variable pitch helix in the direction of the actuation axis 8 and defines a non-linear rotation-translation transformation law.

[0067] According to an embodiment, at least one ramp 103 is configured to limit the movement of the ball 29 in the radial direction.

[0068] Advantageously, this avoids the risk of at least one ball 29 falling off the corresponding ramp 103 .

[0069] According to an advantageous embodiment, the rolling balls 29 are further accommodated by a storage cage 30 interposed between the first ramp portion 101 and the second ramp portion 102, i.e. between the rotor body 23 and the screw body 5, and advantageously supported (rotatably) on the drive shaft 24.

[0070] According to an embodiment, the containment cage 30 forms radially open or closed surrounding vanes 104 or ball seats to prevent the rolling balls 29 from escaping radially.

[0071] According to the embodiment, the first ramp portion 101, the second ramp portion 102 and the rolling elements (balls) 29 are elastically pressed into mutual contact in the direction of the actuation shaft 8.

[0072] This prevents ball vibration and noise from occurring on the ramp and keeps each component in its intended position.

[0073] According to an embodiment (FIGS. 11A, 11B), the actuation device 1 comprises an axial preload spring 42 configured to axially press the first ramp portion 101 towards the second ramp portion 102, in other words the screw body 5 relative to the rotor body 23. The same axial preload spring 42 may be arranged to apply an axial preload to the assembly of the first motion converter 100 and the torque limiter 10.

[0074] The axial preload spring 42 is supported on the drive shaft 24 (e.g. via a Seeger ring 41) and clamped between the free (front) end portion of the drive shaft 24 (facing the forward movement of the piston 7) and the front wall 20 of the screw body 5 (e.g. a coil spring, one or more Belleville springs in series, or a wave spring).

[0075] According to an embodiment (FIGS. 10, 10A), the drive shaft 24 (formed integrally with the rotor body 23) defines an axial through-hole that accommodates a tie rod 46. The tie rod has a mushroom-shaped or plate-shaped front end that rests axially (opposite to the forward movement of the piston 7) against the front wall 20 of the screw body 5, and a rear end that projects into the internal cavity of the rotor body 23. An axial preload spring 42' (advantageously a Belleville spring, one or more Belleville springs in series, or one or more coil springs) inserted in the tie rod 46 is supported on the tie rod 46, for example by a Seager ring, and may be clamped between the rear end of the tie rod 46 and the bottom of the internal cavity of the rotor body 23, preferably via an intervening (anti-friction) bearing 47.

[0076] Advantageously, the first motion converter 100, the second motion converter 4 and the torque limiter 10 are at least partly, preferably completely, housed in the internal cavity of the piston 7 and therefore occupy the same axial space.

[0077] As a further advantage, the torque limiter 10 is at least partly, preferably completely, housed in the inner cavity of the second motion converter 4, preferably in the inner cavity of the screw body 5, and therefore occupies the same axial space.

[0078] Detailed description of the piston 7 and the second screw-nut motion transducer 4

[0079] According to an embodiment, the piston 7 has a substantially hollow cylindrical shape concentric with the actuation axis 8 and comprises a cylindrical wall 14 defining an outer piston surface 11 and an inner piston surface 12, and a head wall 13 transverse to the side wall 14, formed at the front end of the piston 7 and facing the pads 9 of the disc brake 2 in the actuated state.

[0080] According to a preferred embodiment, the inner piston surface 12 is threaded onto the threaded body 5 to form the second nut and the nut 6 of the threaded motion transducer 4 .

[0081] According to an embodiment, the piston 7 is formed with anti-rotation means, for example one or more radial protrusions 16 slidably accommodated in one or more corresponding guides 16 ′ formed in the cylinder 16 ″ and extending in the direction of the actuation shaft 8 , allowing axial movement and preventing rotation of the piston 7 relative to the cylinder 16 ″.

[0082] According to an embodiment, the protrusion 16 may be formed by a grub screw, preferably made of steel, inserted or screwed into a (threaded) hole 15 in the cylindrical wall 14 and oriented radially relative to the actuation shaft 8 .

[0083] By preventing rotation of the piston 7 around the actuation axis 8 and translation of the screw 5 in the direction of the actuation axis 8, rotation of the screw body 5 threaded into the internal thread of the piston 7 results in translation of the piston 7 along the actuation axis 8.

[0084] According to an embodiment, the cylindrical wall 14 may form, on the side of the head wall 13, a circumferential groove 17 adapted to accommodate a dust seal.

[0085] According to a preferred embodiment, the screw body 5 forms:

[0086] A cylindrical side wall 18 concentric with the actuation shaft 8 and having external threads that mate with the internal threads of the piston 7 .

[0087] A front threaded wall 20 facing the forward direction of the piston 7 and a rear threaded wall 21 opposite the front threaded wall 20.

[0088] Preferably, a coupling seat 19 is arranged radially and axially inwardly relative to the outer thread and accommodates the torque limiter 10 .

[0089] This configuration contributes to further reducing the axial dimension of the device 1 .

[0090] According to an embodiment, the rear threaded wall 21 forms a through-hole 43 which leads into the coupling seat 19 and through which the drive shaft 24 extends into the coupling seat 19 .

[0091] The through hole 43 forms a support part that is rotatable with respect to the rotor body 23 around the screw body 5 as the center.

[0092] The peripheral edge between the thread side wall 18 and the thread front wall 20 is chamfered to facilitate insertion and threading of the thread body 5 into the nut 6 formed by the piston 7 .

[0093] Detailed explanation of torque limiter 10

[0094] According to an embodiment, the torque limiter 10 has one or more, preferably two, jaws 31 rotatably integrally coupled to the screw body 5 and resiliently biased to engage the drive shaft 24 .

[0095] According to an embodiment, the coupling seat 19 forms two abutment surfaces 44 and two lateral guide surfaces 44' diametrically opposed to one another with respect to the actuation shaft 8. The jaw 31 (which may consist of a slide) is accommodated between the lateral guide surfaces 44' and guided radially with respect to the actuation shaft 8. A preloaded elastic element 32, for example a compression spring 33, is arranged between the abutment surfaces 44 and the jaw 31.

[0096] The torsional engagement portions of the jaws 31 and the drive shaft 24 are configured to form a rotationally integral fit by interference (with elastic preload).

[0097] In particular, the torsionally engaging portion of the drive shaft 24 may have two flat, parallel opposing surfaces 38, while the jaw 31 may form a trapezoidal coupling surface 34 facing the drive shaft 24 (FIGS. 8, 8A).

[0098] When the transmission torque is lower than the limit torsional moment, the drive shaft 24 is engaged between the jaws 31, and the jaws 31 can rotate integrally with the drive shaft 24.

[0099] When the limiting torsional moment is exceeded, the drive shaft 24 spreads the jaws apart against the elastic force of the compression spring 33, thereby allowing the rotor body 23 to rotate relative to the screw body 5.

[0100] The torque limiter 10 configured in this manner is easy to maintain and has a simple structure for replacing worn jaws 31 as necessary.

[0101] Advantageously, the torque limiter 10 has two jaws 31 arranged opposite each other with respect to the drive shaft 24 .

[0102] According to an embodiment, each jaw 31 defines a coupling surface 34 facing the drive shaft 24 and a biasing surface 35 against which a spring element 32 acts to bias the jaw 31 relative to the drive shaft 24 .

[0103] Advantageously, the biasing surface 35 forms a seat 40 for receiving the end of the elastic element 32 .

[0104] According to a further embodiment, the bonding surface 34 has a substantially planar central surface 36 arranged between two walls or receiving surfaces 37 extending laterally or inclined relative to the biasing surface 35, such that the bonding surface 34 is formed in the form of a trapezoidal or polygonal open channel.

[0105] According to an embodiment, the coupling portion of the drive shaft 24 forms two substantially planar contrasting surfaces 38 disposed between two opposing curved cylindrical or elliptical segment surfaces 39 .

[0106] Advantageously, the transition area between the contrast surface 38 and the curved surface 39 of the shaft 24 is beveled (lacking an internal angle) or chamfered to reduce local contact pressure and thus wear on the surfaces. Furthermore, this allows the jaws 31 to be made of a material that is less hard than the material of the shaft 24.

[0107] In the engagement configuration between drive shaft 24 and jaw 31, a central surface 36 of jaw 31 contacts a corresponding counter surface 38 of drive shaft 24, and a receiving wall or surface 37 of jaw 31 encompasses drive shaft 24 with a curved surface 39.

[0108] Unintentional axial escape of jaw 31 from coupling seat 19 is prevented by the front end of the mushroom-shaped head of tie rod 46 (FIG. 10) or spring 42 (FIGS. 11A, 11B) holding jaw 31 within the space between the mushroom-shaped head or spring 42 and an abutment wall 45 formed within screw body 5, thereby at least partially blocking the outer passage.

[0109] According to an embodiment (FIG. 3), the actuating device 1 comprises a retaining ring 41 (e.g. a steel Seger ring) fixed to the drive shaft 24, which holds the jaw 31 between the retaining ring 41 and the abutment wall 45 of the screw body 5, preventing the jaw 31 from being released from the coupling seat 19.

[0110] According to an alternative embodiment (FIGS. 13A, 13B), the torque limiter 10 comprises a torsion spring 51, for example a coil spring, connected between the first ramp portion 101 and the second ramp portion 102 of the first motion converter 100.

[0111] The moment deformation curve of the torsion spring 51 is selected so that below a predetermined limit torque, the plate-shaped coil spring 51 substantially integrally rotates the first ramp portion 101 and the second ramp portion 102, and above the predetermined limit torque, the torsion spring 51 is gradually deformed to allow relative rotation of the first ramp portion 101 with respect to the second ramp portion 102.

[0112] According to the embodiment, a first end of the torsion spring 51 is integrally connected to the rotor body 23 , in particular to the drive shaft 24 , and a second end of the torsion spring 51 is integrally connected to the screw body 5 .

[0113] According to an embodiment, the predetermined limit torque is between 800 Nmm and 400 Nmm, preferably between 690 Nmm and 490 Nmm, more preferably between 640 Nmm and 540 Nmm, more preferably the predetermined limit torque is 590 Nmm.

[0114] Advantageously, this amount of predetermined limiting torque prevents the occurrence of phenomena of instability or irregularity in the braking torque generated by the disc brake 2 .

[0115] Disc Brake 2 Explained

[0116] In a known manner, the disc brake 2 comprises a caliper including two spaced apart side walls defining a disc space for accommodating a brake disc portion, means for fixing the caliper to the vehicle, a connecting structure extending across the disc space and connecting the side walls to each other, at least one pad seat formed on each of said side walls and adapted to accommodate at least one friction pad, and thrust means bounded by one or both side walls and adapted to bias and clamp the friction pad against the brake disc.

[0117] According to the invention, the thrust means constitute the actuation device 1 described herein.

Claims

1. An actuating device (1) for a brake disc (2), said actuating device (1) comprising: a piston (7) supported slidably along an actuation shaft (8); A first ramp ball motion converter (100), a first ramp portion (101) that is axially constrained and operable to rotate around an operating axis (8); a second ramp portion (102) coupled to the piston (7) and facing the first ramp portion (101); a plurality of rotating elements (29) interposed in contact with a ramp (103) formed by the first ramp portion (101) and the second ramp portion (102); a first ramp ball motion converter (100) such that rotation of the first ramp (101) relative to the second ramp (102) results in damped translation of the second ramp (102) along the actuation axis (8) together with the piston (7) relative to the first ramp (101); a second screw and nut motion converter (4) coupled between the second ramp portion (102) and the piston (7) such that rotation of the second ramp portion (102) relative to the piston (7) about the actuation axis (8) causes a compensating movement of the piston (7) relative to the second ramp portion (102) along the actuation axis (8); A torque limiter (10), comprising: a torsional connection is established between the first ramp portion (101) and the second ramp portion (102), and the first ramp portion (101) and the second ramp portion (102) rotate together about the operating shaft (8) until a predetermined limit torque for the torsional connection is reached; a torque limiter (10) that cuts off rotation of the first ramp portion (101) relative to the second ramp portion (102) about the operating shaft (8) when the torque exceeds the predetermined limit torque, the first ramp portion (101) is formed by a rotor body (23); The rotor body (23) a rotor front wall (26) facing the forward direction of the piston (7) and forming one or more first rolling tracks (28) of the ramp (103); an actuation device (1) having a drive shaft (24) that protrudes from the rotor front wall (26), is coaxial with the operating shaft (8), and is connected to the torque limiter (10), and the second ramp portion (102) is rotatably supported at the center of the drive shaft (24).

2. 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 piston (7) a cylindrical wall (14) having a threaded piston inner surface (12) threaded onto the screw body (5) to form a nut (6) of the second screw and nut motion converter (4); 3. The actuating device (1) according to claim 2, further comprising an anti-rotation means for preventing rotation of the piston (7) about the actuating axis (8).

4. The screw body (5) a cylindrical side wall (18) concentric with the actuation shaft (8) and having an external thread that mates with the internal thread of the piston (7); a front thread wall (20) facing the forward movement direction of the piston (7) and a rear thread wall (21) opposite the front thread wall (20), the rear thread wall (21) forming one or more second rolling tracks (22) of the ramp (103); 4. The actuation device (1) according to claim 3, further comprising a coupling seat (19) extending radially and axially inwardly relative to the external thread and accommodating the torque limiter (10).

5. The screw rear wall (21) forms a through hole (43) that opens into the connecting seat (19), The drive shaft (24) extends into the connecting seat (19) through the through hole (43), 5. The actuation device (1) according to claim 4, wherein the through hole (43) supports the screw body (5) rotatably about the rotor body (23).

6. A bearing assembly (105) supports the rotor body (23) concentrically in axial contact with the operating shaft (8), The actuation device (1) according to claim 4, wherein the bearing assembly (105) is disposed inside the rotor body (23).

7. 5. The actuation device (1) according to claim 4, wherein the rotating element (29) is further housed by a storage cage (30) interposed between the first ramp portion (101) and the second ramp portion (102) and supported on the drive shaft (24).

8. An actuating device (1) as described in any one of claims 4 to 7, wherein the first ramp portion (101), the second ramp portion (102) and the rotating element (29) are elastically pressed into contact with each other in the direction of the actuating axis (8).

9. An actuating device (1) as described in claim 8, comprising an axial preload spring (42) configured to axially press the assembly of the first ramp ball motion converter (100) and the torque limiter (10).

10. An actuating device (1) as described in claim 9, wherein the axial preload spring (42) is supported on the drive shaft (24) and clamped between the free end of the drive shaft (24) and the thread front wall (20) of the screw body (5).

11. The drive shaft (24) defines an axial through-hole for accommodating a tie rod (46), The tie rod (46) an enlarged front end portion axially seated against the thread front wall (20) of the screw body (5); a rear end portion projecting into the internal cavity of the rotor body (23), 5. The actuation device (1) according to claim 4, wherein an axial preload spring (42') is sandwiched between the rear end portion of the tie rod (46) and a bottom surface of the internal cavity of the rotor body (23) with a rolling bearing (47) interposed therebetween.

12. An actuating device (1) as described in any of claims 4 to 11, 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 within the inner piston cavity (7).

13. An actuating device (1) as described in any of claims 4 to 12, wherein the torque limiter (10) is at least partially or completely housed in an inner cavity of the screw body (5) of the second screw and nut motion converter (4).

14. The torque limiter (10) The second ramp portion (102) is coupled to the connecting seat (19) in a rotationally fixed state, 14. An actuation device (1) as claimed in any one of claims 4 to 13, comprising one or more jaws (31) resiliently biased to engage a drive shaft (24) formed on the first ramp portion (101).

15. An actuating device (1) as described in claim 4, wherein the torque limiter (10) has one or more jaws (31) that are rotationally fixedly connected to the screw body (5) and resiliently biased to engage with the drive shaft (24) of the rotor body (23).

16. The connecting seat (19) forms two abutment surfaces (44) and two side guide surfaces (44') that are radially opposed to each other with respect to the operating shaft (8), The jaws (31) are accommodated between the side guide surfaces (44') and are guided radially relative to the working shaft (8); 16. An actuation device (1) according to claim 14 or 15, wherein a preloaded elastic element (32) is arranged between the abutment surface (44) and the jaw (31).

17. An actuating device (1) as described in any one of claims 14 to 16, wherein the torque limiter (10) has two jaws (31) arranged opposite each other with respect to the drive shaft (24).

18. A disc brake (2), a caliper having two spaced-apart side walls defining a disc space for receiving a brake disc portion; 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 pad seat formed on each of the side walls and configured to receive at least one friction pad; and thrust means constrained to one or both of the side walls and configured to clamp the friction pad against the brake disc; A disc brake, wherein the thrust means comprises an actuating device (1) according to any one of claims 1 to 17.

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