Actuation device for a disc brake

Abstract

The present invention relates to a linear actuation device (1) for a disc brake (2), comprising: a recirculating ball screw-nut screw assembly (3) comprising a threaded shaft (7) and a nut screw (8) externally connected to the threaded shaft (7), wherein the threaded shaft (7) and nut screw (8) extend in the direction of an actuation axis (9) coaxial with the threaded shaft (7), and wherein the threaded shaft (7) is at least partially hollow in the axial direction, and a thrust plate (4, 4') configured to receive a braking force generated by a translation of the threaded shaft (7) induced by a rotation of the nut screw (8), said thrust plate (4, 4') being configured to discharge said braking force onto a pad (20) of the disc brake (2), wherein said thrust plate (4, 4') comprises a front wall (22, 220) facing a pad (20) of the disc brake (2), a rear wall (23, 230) facing the threaded shaft (7), and a plate portion (24, 240) which extends from the rear wall (23, 230) into the threaded shaft (7) ending with an end surface (25, 250), said plate portion (24, 240) comprising an outer wall (26, 260) which extends in the axial direction, wherein said linear actuation device (1) further comprises: a joint element (5, 5') interposed in the axial direction between the threaded shaft (7) and the plate portion (24, 240), said joint element (5, 5') being configured to couple spherically with said end surface (25, 250) of the plate portion (24, 240), and a damper (6) interposed in the radial direction between the threaded shaft (7) and the plate portion (24, 240), said damper (6) being configured to couple with the outer wall (26, 260) of the plate portion (24, 240).

Description

[0001] ACTUATION DEVICE FOR A DISC BRAKE

[0002] Description

[0003] Field of the invention

[0004] The present invention relates to a linear actuation device for a disc brake , in particular for an electromechanical disc brake , as well as to a disc brake provided with such an actuation device .

[0005] Background art

[0006] Linear actuation devices for disc brakes are known which comprise a gearmotor associated with a recirculating ball screw-nut screw assembly, formed by a threaded shaft and a nut screw, which converts the torque generated by the gearmotor into a braking force directed against the pads of the disc brake . The braking force , or clamping force , is the force applied by the actuation device to the pads , which act on the disc and, by friction, reduce or stop the rotation thereof .

[0007] It is known to apply the torque generated by the gearmotor to the threaded shaft so as to induce a translation of the nut screw in the direction of the pads of the brake disc and thus generate the braking force . It is also known to apply the torque generated by the gearmotor to the nut screw so as to induce a translation of the threaded shaft in the direction of the pads of the disc brake , generating the braking force . Known linear actuation devices comprise a thrust plate configured to receive a braking force from the recirculating ball screw- nut screw assembly and discharge such a braking force onto a pad of the disc brake .

[0008] During braking, the pad of the disc brake moves tangentially with respect to the linear actuation device and, due to the tangential movement of the pad, the linear actuation device is loaded with a tangential load equal to the clamping force between the pad and the thrust plate multiplied by the coef ficient of friction p between the disc and the pad of the disc brake .

[0009] This tangential load inevitably increases the stress on the linear actuation device , causing an overdesign of said actuation device with respect to a system with axial load only .

[0010] Therefore , the problem underlying the present invention is to provide a linear actuation device for an electromechanical disc brake with a reduced tangential load, i . e . , where the trans fer of the tangential force from the pad onto the recirculating ball screw-nut screw assembly is as small as possible .

[0011] Summary of the invention

[0012] The problem stated above is solved by a linear actuation device as outlined in the appended claims , the definitions of which form an integral part of the present description .

[0013] A first obj ect of the present invention is a linear actuation device for a disc brake , comprising : a recirculating ball screw-nut screw assembly comprising a threaded shaft and a nut screw externally connected to the threaded shaft , wherein the threaded shaft and the nut screw extend in the direction of an actuation axis coaxial with the threaded shaft , and wherein the threaded shaft is at least partially hollow in the axial direction, and a thrust plate configured to receive a braking force generated by a translation of the threaded shaft induced by a rotation of the nut screw, said thrust plate being configured to discharge said braking force onto a pad of the disc brake , said linear actuation device being characterized in that : said thrust plate comprises a front wall facing a pad of the disc brake , a rear wall facing the threaded shaft , and a plate portion which extends from the rear wall into the threaded shaft ending with an end surface , said plate portion comprising an outer wall which extends in the axial direction, said linear actuation device further comprises : a j oint element interposed in the axial direction between the threaded shaft and the plate portion, said j oint element being configured to spherically couple with the end surface of the plate portion, and a damper interposed in the radial direction between the threaded shaft and the plate portion, said damper being configured to couple with the outer wall of the plate portion .

[0014] A further obj ect of the invention is a disc brake comprising a caliper, comprising two mutually spaced apart side walls which delimit a disc space to accommodate a portion of a brake disc, means for fixing the caliper to a vehicle , a connection structure which extends straddling the disc space and connects the side walls to each other, at least one pad seat formed in each of said side walls and adapted to accommodate at least one pad, thrust means constrained to one or both s ide walls and adapted to bias the pads against the brake disc to clamp it , wherein the thrust means comprise the actuation device as described above .

[0015] The linear actuation device of the present invention advantageously allows decoupling the tangential forces discharged during braking from the pad of the di sc brake to the linear actuation device . In order to better understand the invention and appreciate the advantages thereof , some non-limiting exemplary embodiments thereof will be described below with reference to the accompanying drawings .

[0016] Brief description of the figures

[0017] Figure 1 is a side view, along an axial section, of a caliper for a disc brake according to a first embodiment of the present invention .

[0018] Figure 2 is a diagrammatic depiction of the view in Figure 1 , wherein the system consisting of thrust plate , j oint element , and damper of the linear actuation device according to an embodiment of the present invention is shown .

[0019] Figure 3 is a side view, along an axial section, of the system consisting of thrust plate , j oint element , and damper of the linear actuation device according to the first embodiment of the present invention .

[0020] Figures 4A and 4B show the system consisting of thrust plate , j oint element , and damper of Figure 3 , when the clamping force is not applied ( Figure 4A) and when the clamping force is applied ( Figure 4B ) , respectively .

[0021] Figure 5 is a side view, along an axial section, of the linear actuation device according to the first embodiment of the present invention, in which the antirotation pin is not shown . Figure 6 is an exploded view of the linear actuation device shown in Figure 5 .

[0022] Figure 7 is an exploded perspective view of the linear actuation device for a disc brake according to the first embodiment of the present invention .

[0023] Figure 8 is a side view, along an axial section, of a caliper for a disc brake according to a second embodiment of the present invention .

[0024] Figure 9 is a diagrammatic depiction of the view in Figure 8 , wherein the system consisting of thrust plate , j oint element , and damper of the linear actuation device according to an embodiment of the present invention is shown .

[0025] Figure 10 is a side view, along an axial section, of the system consisting of thrust plate , j oint element , and damper of the linear actuation device according to the second embodiment of the present invention .

[0026] Figures 11A and 11B show the system consisting of thrust plate , j oint element , and damper of Figure 10 , when the clamping force is not applied ( Figure 11A) and when the clamping force is applied ( Figure 11B ) , respectively .

[0027] Figure 12 is a side view, along an axial section, of the linear actuation device according to the second embodiment of the present invention, in which the antirotation pin is not shown . Figure 13 is an exploded view of the linear actuation device shown in Figure 12.

[0028] Figure 14 is an exploded perspective view of the linear actuation device for a disc brake according to the second embodiment of the present invention.

[0029] Figures 15A, 15B and 15C show the damper according to an embodiment of the present invention, respectively, in a perspective view, a top view, and a side view, the latter along an axial section.

[0030] Figure 16 is a side perspective view of the linear actuation device for a disc brake, according to an embodiment of the present invention.

[0031] Detailed description of the invention

[0032] In the following description, the term "front" orientation refers to the orientation of sides, faces, surfaces, etc., in the advancement (braking) direction of the threaded shaft, the term "rear" orientation refers to the orientation of sides, faces, surfaces, etc., in the retraction direction of the threaded shaft, unless otherwise specified. The terms "radial", "circumferential", "axial" should be intended with respect to the actuation axis of the threaded shaft, unless otherwise specified. "Translation" and "rotation" with respect to the actuation axis or with respect to the axial direction denote a translation or a rotation with respect to an axis which is integral in rotation with the threaded shaft of the recirculating ball screw-nut screw assembly and which is integral in translation with the recirculating ball screw-nut screw assembly . "Axial direction" denotes a direction parallel to or coincident with the actuation axis .

[0033] In the following description, the wording " coaxial with the recirculating ball screw-nut screw assembly" referred to the plate portion 24 , 240 , the j oint element 5 , 5 ' , the pin 31 , 310 , and the damper 6 , as defined below, denotes that such elements are coaxial with the screw-nut screw assembly when the braking force is not applied .

[0034] With reference to the figures , an actuation device 1 for a disc brake 2 comprises a recirculating ball screw- nut screw assembly 3 , a thrust plate 4 , 4 ' , a j oint element 5 , 5 ' , and a damper 6 .

[0035] The recirculating ball screw-nut screw assembly 3 comprises a threaded shaft 7 and a nut screw 8 externally connected to the threaded shaft 7 .

[0036] The threaded shaft 7 and the nut screw 8 extend in the direction of an actuation axis 9 coaxial with the threaded shaft 7 .

[0037] The threaded shaft 7 extends between a front end thereof and a rear end thereof . The threaded shaft 7 forms a front shaft wall 10 at the front end thereof and a rear shaft wall 11 at the rear end thereof .

[0038] Advantageously, the nut screw 8 is configured to receive a torque generated by a gearmotor (not shown) , and a rotation of the nut screw 8 with respect to the threaded shaft 7 results in a translation of the threaded shaft 7 with respect to the nut screw 8 in the direction of the actuation axis 9 .

[0039] According to an embodiment , the nut screw 8 forms an external toothing 12 configured to receive a torque from the gearmotor .

[0040] According to an embodiment , the threaded shaft 7 is at least partially hollow in the axial direction and forms an inner wall 13 . The inner wall 13 defines a cavity 14 .

[0041] According to an embodiment , said cavity 14 extends between a front opening 15 , defined at the front shaft wall 10 , and a rear opening 16 , defined at the rear shaft wall 11 .

[0042] According to an embodiment , the inner wall 13 of the threaded shaft 7 forms an abutment step 17 .

[0043] According to an embodiment , the abutment step 17 delimits a first cavity portion 18 ( front portion) , extending between the abutment step 17 and the front opening 15 , and a second cavity portion 19 ( rear portion) , extending between the abutment step 17 and the rear opening 16. Advantageously, the first cavity portion 18 has a radial section which is greater than the radial section of the second cavity portion 19.

[0044] The first cavity portion 18 is adapted to accommodate the joint element 5, 5', the damper 6 and, partially, the thrust plate 4, 4' . As will be apparent in the following description, the first cavity portion 18 is adapted to accommodate the joint element 5, 5', the damper 6, and the plate portion 24, 240.

[0045] The second cavity portion 19 is adapted to accommodate an anti-rotation pin 21. In the embodiment shown in the figures, the second cavity portion 19 does not have the same radial section along the entire axial extension thereof, but the radial section thereof is greater at the rear shaft wall 11 in order to accommodate the antirotation pin 21.

[0046] The anti-rotation pin 21 is configured to allow a translation of the threaded shaft 7 in the axial direction and prevent a rotation of the threaded shaft 7 about the axial direction. Therefore, the anti-rotation pin 21 is configured to prevent the rotation of the nut screw 8 from driving the threaded shaft 7 into rotation.

[0047] The thrust plate 4, 4' is operatively connected to the recirculating ball screw-nut screw assembly 3. The thrust plate 4 is configured to receive a braking force from the threaded shaft 7. Said braking force is generated by a translation of the threaded shaft 7 induced by a rotation of the nut screw 8.

[0048] Advantageously, the thrust plate 4, 4' is configured to discharge said braking force onto a pad 20 of the disc brake 2.

[0049] Advantageously, the thrust plate 4, 4' is configured to distribute the braking force, or clamping force, onto the pad 20 of the disc brake 2.

[0050] The thrust plate 4, 4' comprises a front wall 22, 220 facing the pad 20 of the disc brake 2, a rear wall 23, 230 facing the threaded shaft 7, and a plate portion 24, 240 which extends from the rear wall 23, 230 into the threaded shaft 7 ending with an end surface 25, 250. More in particular, said plate portion 24, 240 extends into the first cavity portion 18 of the threaded shaft 7.

[0051] According to different embodiments, said end surface 25, 250 is either concave (first embodiment) or convex (second embodiment) with respect to the joint element 5, 5' with which it couples spherically. As a result, as will become apparent from the description below, in the first embodiment the joint element 5 spherically couples with the concave surface 25 of the plate portion 24 through a convex surface, while in the second embodiment the joint element 5' spherically couples with the convex surface 250 of the plate portion 240 through a concave surface.

[0052] Advantageously, the spherical coupling between the joint element 5, 5' and the end surface 25, 250 of the plate portion 24, 240 is a coupling between concave / convex surfaces .

[0053] The joint element 5, 5' is interposed in the axial direction between the threaded shaft 7 and the aforesaid plate portion 24, 240, while the damper 6 is interposed in the radial direction between the threaded shaft 7 and said plate portion 24, 240.

[0054] The plate portion 24, 240 comprises an outer wall 26, 260 which extends in the direction of the actuation axis 9 and is coaxial with the recirculating ball screw-nut screw assembly 3. According to the embodiments shown in the figures, said outer wall 26, 260 has a cylindrical outer shape.

[0055] First embodiment

[0056] According to a first embodiment of the present invention (shown in Figures 1-7) , the plate portion 24 extends from the rear wall 23 of the thrust plate 4 into the threaded shaft 7 ending in a concave end surface 25.

[0057] According to a preferred embodiment, the plate portion 24 is hollow. According to this embodiment, the plate piston 24 comprises a blind cavity 27. Said cavity 27 is delimited by an inner wall 28 of the plate portion 24 and the aforesaid concave surface 25 of the plate portion 24 . According to this embodiment , said concave surface 25 defines the terminal end of the plate portion 24 in which the cavity 27 opens . According to the embodiment shown in the figures , said concave surface 25 is either annular or substantially annular .

[0058] Advantageously, the j oint element 5 is a ball j oint . Advantageously, the j oint element 5 comprises a front wall 29 abutting, at least partially, against the concave surface 25 of the plate portion 24 , and an opposite planar wall 30 abutting against the abutment step 17 formed by the inner wall 13 of the threaded shaft 7 . Preferably, said planar wall 30 has a circular shape .

[0059] Advantageously, the front wall 29 of the j oint element 5 forms a spherical , or substantially spherical , surface which couples with the corresponding concave surface 25 of the plate portion 24 . More in particular, the front wall 29 of the j oint element 5 forms a convex surface which couples with the corresponding concave surface 25 of the plate portion 24 .

[0060] Advantageously, the j oint element 5 is coaxial with the recirculating ball screw-nut screw assembly 3 .

[0061] According to an embodiment , a pin 31 protrudes from the front wall 29 of the j oint element 5 . Said pin 31 is coaxial with the recirculating ball screw-nut screw assembly 3 , extending in the direction of the actuation axis 9 .

[0062] Preferably, said pin 31 is formed in one piece with the front wall 29 of the j oint element 5 .

[0063] According to the embodiment shown in the figures , said pin 31 comprises a first cylindrical pin portion 32 and a second f rustoconical pin portion 33 . Preferably, said two pin portions 32 , 33 are formed in one piece . Preferably, the first cylindrical pin portion 32 protrudes from the aforesaid front wall 29 , thus resulting interposed between the latter and the second f rustoconical pin portion 33 .

[0064] In an alternative embodiment , said pin 31 is cylindrical .

[0065] Advantageously, said pin 31 extends into the blind cavity 27 of the plate portion 24 . Since , according to this embodiment , the j oint element 5 is partially positioned inside the blind cavity 27 , said cavity is also referred to as j oint seat 27 .

[0066] With added advantage , said pin 31 is positioned in a flexible or sliding manner inside the j oint seat 27 . Preferably, the j oint seat 27 comprises at least one seat portion having a radial section which is greater than the section of the pin 31 and into which the pin itsel f is inserted .

[0067] According to an embodiment , not shown, the j oint seat 27 is a cylindrical seat with a constant radial section . Advantageously, said radial section is greater than the section of the pin 31 and the latter is positioned in a flexible or sliding manner inside the j oint seat 27 .

[0068] According to another embodiment , shown in the figures , the inner wall 28 of the plate portion 24 forms an abutment step 34 , which delimits a first portion 35 of the j oint seat 27 , into which the aforementioned pin 31 is inserted, and a second portion 36 of the j oint seat 27 ; said second portion 36 of the j oint seat 27 has a smaller radial section than the first portion 35 of the j oint seat 27 .

[0069] According to this embodiment , advantageously, said first portion 35 of the j oint seat 27 has a radial section which is greater than the section of said pin 31 , more in particular greater than both the section of said first cylindrical portion 32 and of said second f rustoconical portion 33 . Advantageously, the pin 31 of the j oint element 5 is thus positioned in a flexible or sliding manner inside said first portion 35 of the j oint seat 27 .

[0070] Second embodiment According to a second embodiment of the present invention (shown in Figures 8-14) , the plate portion 240 extends from the rear wall 230 of the thrust plate 4' into the threaded shaft 7 ending in a convex end surface 250.

[0071] Advantageously, the joint element 5' comprises a front wall 290 abutting, at least partially, against the convex surface 250 of the plate portion 240, and an opposite planar wall 300 abutting against the abutment step 17 formed by the inner wall 13 of the threaded shaft 7.

[0072] Advantageously, the front wall 290 of the joint element 5' forms a spherical, or substantially spherical, surface which couples with the corresponding convex surface 250 of the plate portion 240. More in particular, the front wall 290 of the joint element 5' forms a concave surface which couples with the corresponding convex surface 250 of the plate portion 240.

[0073] According to a preferred embodiment, said joint element 5' is hollow and defines a cavity 270. Preferably, said cavity 270 is a through-cavity. Said cavity 270 is delimited by an inner wall 280 of the joint element 5' and by the aforesaid concave wall 290 of the joint element 5' .

[0074] According to the embodiment shown in the figures, said concave wall 290 is annular, or substantially annular, and said inner wall 280 is cylindrical , or substantially cylindrical .

[0075] According to the embodiment shown in the figures , the j oint element 5 ' is annular in shape . According to this embodiment , said concave wall 290 and said opposite planar wall 300 are annular, or substantially annular, and said inner wall 280 is cylindrical , or substantially cylindrical .

[0076] Advantageously, said j oint element 5 ' is coaxial with the recirculating ball screw-nut screw assembly 3 .

[0077] According to an embodiment , a pin 310 protrudes from the end surface 250 of the plate portion 240 . Said pin 310 is coaxial with the recirculating ball screw-nut screw assembly 3 , extending in the direction of the actuation axis 9 .

[0078] Preferably, said pin 310 is formed in one piece with the end surface 250 of the plate portion 240 .

[0079] According to the embodiment shown in the figures , said pin 310 comprises a first cylindrical pin portion 320 and a second f rustoconical pin portion 330 . Preferably, said two pin portions 320 , 330 are formed in one piece . Preferably, the first cylindrical pin portion 320 protrudes from the aforesaid end surface 250 , thus being interposed between the latter and the second f rustoconical pin portion 330 . In an alternative embodiment , said pin 310 is cylindrical .

[0080] Advantageously, said pin 310 extends into the cavity 270 of the j oint element 5 ' . According to this embodiment , the plate portion 240 is partially positioned inside the cavity 270 .

[0081] With added advantage , said pin 310 is positioned in a flexible or sliding manner inside the cavity 270 . Preferably, the cavity 270 comprises at least one cavity portion having a radial section which is greater than the section of the pin 310 and into which the pin itsel f is inserted .

[0082] According to the embodiment shown, the cavity 270 is cylindrical with constant radial section . Advantageously, said radial section is greater than the section of the pin 310 and the latter is positioned in a flexible or sliding manner inside the cavity 270 . In both the aforesaid embodiments , advantageously, the surface extension of the planar wall 30 , 300 of the j oint element is smal ler than the section of the first cavity portion 18 and greater than the section of the second cavity portion 19 .

[0083] Advantageously, when the clamping force is applied, the thrust plate 4 , 4 ' undergoes an inclination equal to an angle a, and the planar wall 30 , 300 , thus the j oint element 5, 5', can slide freely on the abutment step 17 (Figures 4B and 11B) .

[0084] Advantageously, the presence of said joint element 5, 5' ensures low friction with the threaded shaft 7, resulting in a reduction of the tangential force transmitted during braking from the pad 20 towards the linear actuation device 1.

[0085] Advantageously, the joint element 5, 5' acts as a decoupler between the recirculating ball screw-nut screw assembly 3 and the thrust plate 4, 4' in case of radial load peaks coming from the contact between the thrust plate 4, 4' and the pad 20 of the disc brake 2.

[0086] With added advantage, the joint element 5, 5' is such as to allow and accommodate rotational and / or translatory displacements of the thrust plate 4, 4' with respect to the threaded shaft 7.

[0087] As mentioned above, the damper 6 is interposed in the radial direction between the threaded shaft 7 and the plate portion 24, 240. More in particular, the damper 6 is positioned inside the threaded shaft 7 between the plate portion 24, 240 and the inner wall 13 of the threaded shaft 7.

[0088] Advantageously, the damper 6 is coaxial with the plate portion 24, 240 and the threaded shaft 7. Advantageously, the damper 6 is coaxial with the recirculating ball screw- nut screw assembly 3 .

[0089] In particular, the damper 6 is positioned in the cavity 14 of the threaded shaft 7 , more in particular, in the first cavity portion 18 as defined above .

[0090] Advantageously, the damper 6 is annular in shape . Advantageously, the damper 6 defines a central cavity 37 into which said plate portion 24 , 240 is inserted . Advantageously, said central cavity 37 is delimited by an inner wall 38 of the damper 6 configured to couple with the outer wall 26 , 260 of the plate portion 24 , 240 . Advantageously, the inner wall 38 of the damper 6 and the outer wall 26 , 260 of the plate portion 24 , 240 are cylindrical , and the coupling between the damper 6 and the plate portion 24 , 240 is a cylindrical coupling .

[0091] According to an embodiment , said plate portion 24 , 240 has a radial section which i s smaller than the first cavity portion 18 in which it is positioned, resulting in the presence of an annular space 39 between said plate portion 24 , 240 and the inner wall 13 of the threaded shaft 7 . According to this embodiment , the damper 6 is positioned in said annular space 39 , thus being interposed between the plate portion 24 , 240 and the threaded shaft 7 . Said annular space 39 is the space inside which the thrust plate 4, 4' moves; in other words, it represents the motion range of the thrust plate 4, 4' .

[0092] According to the embodiment shown in the figures, the damper 6 has an extension in the axial direction which is smaller than the first cavity portion 18 of the threaded shaft 7.

[0093] In addition to the aforementioned inner wall 38, advantageously, the damper 6 comprises an outer wall 42, or edge wall 42. Said walls 38, 42 determine the thickness of the damper 6 along the actuation axis 9, while the distance between said walls 38, 42 determines the thickness of the damper 6 in the radial direction.

[0094] According to an embodiment, said walls 38, 42 are connected to each other by an annular wall 40 perpendicular thereto. Preferably, said annular wall 40 is positioned in the middle of the axial extension of the walls 38, 42, i.e., it is equidistant from the ends of the inner wall 38 and the outer wall 42. According to this embodiment, the damper 6 has a front concavity 41a facing the thrust plate 4 and a rear concavity 41b facing the threaded shaft 7, each concavity 41a, 41b being delimited by the inner and outer walls 38, 42 and by the annular wall 40.

[0095] According to an embodiment, the outer wall 42 has a concavity 43a which extends circumferentially, preferably in the central part of said outer wall 42, preferably said central part being equidistant from the ends of the outer wall 42 .

[0096] According to this embodiment , due to the presence of the aforementioned concavity 43a, the damper 6 has - at the central portion thereof - a radial extension such that there is a gap between the outer wall 42 of the damper 6 and the inner wall 13 of the threaded shaft 7 and - at the two ends or peripheral portions - a radial extension such that the outer wall 42 contacts the inner wall 13 of the threaded shaft 7 .

[0097] According to an embodiment , the inner wall 38 has a concavity 43b which extends circumferentially, preferably in the central part of said inner wall 38 , preferably said central part being equidistant from the ends of inner wall 38 .

[0098] According to this embodiment , due to the presence of the aforesaid concavity 43b, the damper 6 has - at the central part thereof - a radial extension such that there is a gap between the inner wall 38 of the damper 6 and the outer wall 26 , 260 of the plate portion 24 , 240 and - at the two ends or peripheral portions - a radial extension such that the outer wall 38 contacts the outer wall 26, 260 of the plate portion 24 , 240 . According to a preferred embodiment , both the outer wall 42 and the inner wall 38 have the aforesaid concavity 43a, 43b .

[0099] According to a preferred embodiment , the axial section of the damper 6 is substantially "X" -shaped ( Figure 9C ) .

[0100] Such a configuration of the damper 6 is advantageous because it allows , at the central part of the damper 6 , to support the movement of the thrust plate 4 , 4 ' in a more rigid manner, absorbing the tangential force by means of its elastic deformation . Furthermore , when the thrust plate 4 , 4 ' undergoes an inclination equal to an angle a, advantageously, the central part of the damper 6 wi ll act as a fulcrum and will deform the most peripheral portions .

[0101] Advantageously, the damper 6 has a radial extension such as to occupy entirely, or substantially entirely, the annular space 39 in the radial direction . The wording " substantially entirely" refers to the embodiment described above in which the central part of the damper 6 has at least one concavity 43a, 43b, thus the damper 6 has a radial extension such as to occupy entirely the annular space 39 in the radial direction only at the two peripheral portions thereof .

[0102] Even more advantageously, the damper 6 is compressible inside said annular space 39 . According to this embodiment, the thickness of the damper 6 in the radial direction, i.e., the radial extension thereof, when it is not inserted into the annular space 39, is equal to or greater than the radial extension of the annular space 39. According to the embodiment in which the central part of the damper 6 has at least one concavity 43a, 43b, advantageously, the radial extension of the peripheral portions of the damper 6 only is equal to or greater than the radial extension of the annular space 39, when the damper is not inserted into the annular space 39.

[0103] Preferably, the damper 6 has a force value between 0 and 500 N.

[0104] According to an embodiment, the damper 6 comprises a plurality of axial channels 54, or axial through holes 54, obtained in the outer wall 42, which thus has a plurality of recesses. Preferably, said axial channels 54 extend over the entire axial extension of the outer wall 42 of the damper.

[0105] According to different embodiments, the damper 6 can comprise from 2 to 8 axial channels 54, e.g., 3, 4, 5, 6, 7, preferably equidistant.

[0106] In the embodiment shown in Figs. 15A-15C, the damper 6 comprises three axial channels 54 which are equidistant. According to this embodiment, the axial channels 54 are positioned at 120°. Advantageously, the presence of the damper 6 ensures the positioning of the thrust plate 4, 4' when the clamping force is not applied. More in particular, the presence of the damper 6 causes the thrust plate 4, 4' to be positioned on the actuation axis 9; in the absence of the damper 6, the thrust plate 4, 4' would move inside the threaded shaft 7.

[0107] Advantageously, the damper 6 allows reducing the rattle noise of the thrust plate 4, 4' and the joint element 5, 5 ' .

[0108] With added advantage, the damper allows a tangential movement of the thrust plate 4, 4' .

[0109] Under the clamping force and the rotation of the disc 45, the thrust plate 4, 4' and the joint element 5, 5' are constrained together to translate with the pad 20 by virtue of the presence of the damper 6, which also absorbs the tangential force by means of the elastic deformation thereof. After braking, the damper 6 returns the joint element 5, 5' and the thrust plate 4, 4' to the starting position; this effect is maximized by the planar wall 30 of the joint element 5, 5' facing the linear transmission system, which allows the relative sliding.

[0110] The above-described configuration of the system consisting of thrust plate 4, 4', joint element 5, 5', and damper 6 allows said system to take an inclination angle a, when the clamping force is applied, avoiding the exchange of tangential forces towards the linear actuation system 1 and the generation of unbalanced loads acting on the recirculating ball screw-nut screw assembly 3, in turn compensating for the deformation of the caliper body 44 under the action of the clamping force.

[0111] Advantageously, the spherical coupling between the thrust plate 4, 4' and the joint element 5, 5' allows the inclination of the thrust plate 4, 4' according to the aforesaid angle a, while the cylindrical coupling between the thrust plate 4, 4' and the damper 6 allows keeping the thrust plate 4, 4' in a stable position at different inclination angles a.

[0112] With added advantage, by virtue of this configuration, the tangential force transmitted from the disc 45 to the pad 20 and from the latter to the thrust plate 4, 4' is discharged onto the caliper 44 of the disc brake 2, instead of onto the linear actuation system 1, thus allowing a reduction in the radial load acting on the recirculating ball screw-nut screw assembly 3.

[0113] According to a preferred embodiment, the thrust plate 4, 4' and the joint element 5, 5' are made of a metal material, preferably steel, or aluminum or alloys thereof, or other light alloys. According to a preferred embodiment , the damper 6 is made of rubber .

[0114] According to an embodiment , the actuation device 1 comprises a force sensor 46 , which is advantageously configured to detect the braking force applied by the actuation device 1 . More in particular, the force sensor 46 is configured to detect the force applied in the axial direction by the actuation device 1 .

[0115] In the embodiment shown in the figures , the force sensor 46 is positioned behind the threaded shaft 7 , preferably placed alongside of the second cavity portion 19 which houses the anti-rotation pin 21 .

[0116] According to various embodiments , the force sensor 46 is substantially cylindrical , discoidal , or axisymmetric in shape .

[0117] According to an embodiment , the actuation device 1 comprises a spacer 47 . Preferably, the spacer 47 is substantially cylindrical in shape .

[0118] According to an embodiment , the spacer 47 is positioned within the axial extension of the threaded shaft 7 .

[0119] In an embodiment , the spacer 47 is coaxial with the threaded shaft 7 and the threaded shaft 7 is positioned passing through the spacer 47 . Advantageously, the spacer 47 is configured to trans fer the clamping force from the nut screw 8 to the anti-rotation pin 21 .

[0120] According to an embodiment , the spacer 47 and the anti-rotation pin 21 slide freely in the body of the caliper 44 , ensuring the correct transmission of the force to the force sensor 46 .

[0121] Advantageously, by detecting the force acting on the spacer 47 , coming from an axial bearing 48 defined below, the force sensor 46 is capable of determining the braking force implemented by means of the actuation device 1 .

[0122] According to an embodiment , the actuation device 1 comprises an axial bearing 48 .

[0123] According to an embodiment , the axial bearing 48 is positioned within the axial extension of the threaded shaft 7 .

[0124] According to an embodiment , the axial bearing 48 is coaxial with the threaded shaft 7 , and the threaded shaft 7 is positioned passing through the axial bearing 48 .

[0125] According to an embodiment , the axial bearing 48 is a ball bearing . Alternatively, the axial bearing 48 is a roller bearing .

[0126] Advantageously, the axial bearing 48 allows the rotation of the nut screw 8 and transmits the clamping force to the spacer 47 . According to an embodiment , the actuation device 1 comprises a radial bearing 49 .

[0127] The radial bearing 49 is configured to support the radial stresses acting on the actuation device 1 and generated by transmission of the torque from the gearmotor to the actuation device 1 .

[0128] According to a preferred embodiment , the radial bearing 49 is connected externally to the nut screw 8 .

[0129] Even more preferably, the radial bearing 49 is placed adj acent to the axial bearing 48 , on the side facing the thrust plate 4 , 4 ' .

[0130] Preferably, the radial bearing 49 is a roller type bearing . Alternatively, the radial bearing 49 is a ball bearing .

[0131] Advantageously, the nut screw 8 rotates inside the radial bearing 49 and transmits the clamping force to the force sensor 46 through the axial bearing 48 , the spacer 47 , and the anti-rotation pin 21 .

[0132] According to an embodiment , the actuation device 1 comprises a gasket or cap 50 ( dust boot ) connected to the thrust plate 4 , 4 ' .

[0133] The cap 50 is configured to make a fluid seal between the actuation device 1 and the pad 20 of the disc brake 2 . Advantageously, the cap 50 protects the mechanical components of the actuation device 1 from contact with dust , moisture , or other contaminants .

[0134] According to an embodiment , the nut screw 8 defines a circumferential seat 51 interposed between the external toothing 12 and the thrust plate 4 , 4 ' . According to this embodiment , the cap 50 is positioned in the circumferential seat 51 .

[0135] According to an embodiment , the thrust plate 4 , 4 ' defines a circumferential groove 52 extending towards the inside of the thrust plate 4 , 4 ' in the radial direction . According to this embodiment , the cap 50 is positioned in the circumferential seat 51 , and one end of the cap 50 is inserted into the circumferential groove 52 .

[0136] According to an embodiment , the actuation device 1 comprises an axial retaining ring 53 .

[0137] The axial retaining ring 53 is positioned external ly to the nut screw 8 .

[0138] Preferably, the axial retaining ring 53 is interposed, optionally with contact , between the cap 50 and the external toothing 12 of the nut screw 8 . Preferably, the axial retaining ring 53 is mounted by interference . The axial retaining ring 53 is configured to hold the actuation device 1 in the predefined position inside the caliper 44 of the disc brake 2 .

[0139] According to an embodiment , one end of the axial retaining ring 53 is positioned against the external toothing 12 of the nut screw 8 in order to prevent a possible disassembly of the actuation device 1 due to the vibrations generated during the actuation of the actuation device 1 . It is apparent that the embodiment described is only one particular embodiment of the present invention . Those skilled in the art will be able to make all the necessary modi fications to the invention for the adaptation thereof to particular conditions , without however departing from the scope of protection as defined in the appended claims .

[0140] List of reference numerals

[0141] 1. Actuation device

[0142] 2. Disc brake

[0143] 3. Recirculating ball screw-nut screw assembly

[0144] 4. Thrust plate

[0145] 4' . Thrust plate

[0146] 5. Joint element

[0147] 5' . Joint element

[0148] 6. Damper

[0149] 7. Threaded shaft

[0150] 8. Nut screw

[0151] 9. Actuation axis

[0152] 10. Front shaft wall

[0153] 11. Rear shaft wall

[0154] 12. External toothing of the nut screw

[0155] 13. Inner wall of the threaded shaft

[0156] 14. Cavity of the threaded shaft

[0157] 15. Front opening of cavity 14

[0158] 16. Rear opening of cavity 14

[0159] 17. Abutment step of wall 13

[0160] 18. First cavity portion

[0161] 19. Second cavity portion

[0162] 20. Pad

[0163] 21. Anti-rotation pin

[0164] 22. Front wall of the thrust plate

[0165] 23. Rear wall of the thrust plate

[0166] 24. Plate portion

[0167] 25. Concave surface of the plate portion

[0168] 26. Outer wall of the plate portion

[0169] 27. Blind cavity (joint seat) . Inner wall of the plate portion . Front wall of the j oint element . Planar wall of the j oint element . Pin . First cylindrical pin portion . Second f rustoconical pin portion . Abutment step of the inner wall 28. First portion of the j oint seat . Second portion of the j oint seat . Central cavity of the damper . Inner wall of the damper . Annular space . Annular wall of the damper a . Front concavity of the damper b . Rear concavity of the damper . Outer wall or edge wall of the dampera . Concavity of the outer wall 42 b . Concavity of the inner wall 38 . Caliper . Disc . Force sensor . Spacer . Axial bearing . Radial bearing . Cap ( dust boot ) . Circumferential seat . Circumferential groove . Axial retaining ring . Axial channels 0 . Front wall of the thrust plate 0 . Rear wall of the thrust plate Plate portion

[0170] Convex surface of the plate portion

[0171] Outer wall of the plate portion

[0172] Cavity

[0173] Inner wall of the j oint element

[0174] Front wall of the j oint element

[0175] Planar wall of the j oint element

[0176] Pin

[0177] First cylindrical pin portion

[0178] Second f rustoconical pin portion

Claims

CLAIMS1. A linear actuation device (1) for a disc brake(2) , comprising: a recirculating ball screw-nut screw assembly (3) comprising a threaded shaft (7) and a nut screw (8) externally connected to the threaded shaft (7) , wherein the threaded shaft (7) and nut screw (8) extend in the direction of an actuation axis (9) coaxial with the threaded shaft (7) , and wherein the threaded shaft (7) is at least partially hollow in the axial direction, and a thrust plate (4, 4' ) configured to receive a braking force generated by a translation of the threaded shaft (7) induced by a rotation of the nut screw (8) , said thrust plate (4, 4' ) being configured to discharge said braking force onto a pad (20) of the disc brake (2) , said linear actuation device (1) being characterized in that: said thrust plate (4, 4' ) comprises a front wall (22, 220) facing a pad (20) of the disc brake (2) , a rear wall (23, 230) facing the threaded shaft (7) , and a plate portion (24, 240) which extends from the rear wall (23, 230) into the threaded shaft (7) ending with an end surface (25, 250) , said plate portion (24, 240) comprising an outer wall (26, 260) which extends in the axial direction, said linear actuation device (1) further comprises:a joint element (5, 5' ) interposed in the axial direction between the threaded shaft (7) and the plate portion (24, 240) , said joint element (5, 5' ) being configured to spherically couple with the end surface (25, 250) of the plate portion (24, 240) , and a damper (6) interposed in the radial direction between the threaded shaft (7) and the plate portion (24, 240) , said damper (6) being configured to couple with the outer wall (26, 260) of the plate portion (24, 240) .

2. A linear actuation device (1) according to claim 1, wherein the end surface (25) of the plate portion (24) is concave with respect to the joint element (5) with which it spherically couples, and the joint element (5) comprises a front wall (29) abutting, at least partially, against the concave surface (25) of the plate portion (24) .

3. A linear actuation device (1) according to claim 2, wherein the plate portion (24) comprises a blind cavity (27) delimited by an inner wall (28) of the plate portion (24) and by the concave surface (25) of the plate portion (24) .

4. An actuation device (1) according to claim 3, wherein a pin (31) protrudes from the front wall (29) ofthe joint element (5) , which extends in the axial direction into the blind cavity (27) , preferably, said pin (31) is positioned in a flexible or sliding manner inside the blind cavity (27 ) .

5. An actuation device according to claim 4, wherein said pin (31) comprises a first cylindrical pin portion (32) and a second f rustoconical pin portion (33) , preferably the first cylindrical pin portion (32) is interposed between the front wall (29) of the joint element (5) and the second f rustoconical pin portion (33) .

6. A linear actuation device (1) according to claim 1, wherein the end surface (250) of the plate portion (240) is convex with respect to the joint element (5' ) with which it spherically couples, and the joint element (5' ) comprises a front wall (290) abutting, at least partially, against the convex surface (250) of the plate portion (240) .

7. A linear actuation device (1) according to claim 6, wherein the joint element (5' ) comprises a cavity (270) delimited by an inner wall (280) of the joint element (5' ) and by the front wall (290) of the joint element (5' ) , preferably said cavity (270) being a through-cavity.

8. An actuation device (1) according to claim 7, wherein a pin (310) protrudes from the end surface (250) of the plate portion (240) , which extends in the axial direction into the cavity (270) , preferably, said pin (31) is positioned in a flexible or sliding manner inside the cavity (270) .

9. An actuation device according to claim 8, wherein said pin (310) comprises a first cylindrical pin portion (320) and a second f rustoconical pin portion (330) , preferably the first cylindrical pin portion (320) is interposed between the end surface (250) of the plate portion (240) and the second f rustoconical pin portion(330) .

10. A linear actuation device (1) according to any one of the preceding claims, wherein the threaded shaft (7) forms an inner wall (13) which defines a cavity (14) and forms an abutment step (17) , wherein the abutment step delimits a first front cavity portion (18) and a second rear cavity portion (19) , wherein the first cavity portion (18) has a greater radial section than the radial section of the second cavity portion (19) ,wherein the joint element (5, 5' ) comprises a planar wall (30, 300) abutting against the abutment step (17) formed by the inner wall (13) of the threaded shaft (7) .

11. A linear actuation device (1) according to claim 10, wherein the first cavity portion (18) is adapted to accommodate the plate portion (24, 240) , the joint element (5, 5' ) and the damper (6) , and said second cavity portion (19) is adapted to accommodate an anti-rotation pin (21) .

12. An actuation device according to any one of the preceding claims, wherein the damper (6) defines a central cavity (37) into which the plate portion (24, 240) is inserted, wherein said central cavity (37) is delimited by an inner wall (38) of the damper (6) configured to couple with the outer wall (26, 260) of the plate portion (24, 240) , preferably, the inner wall (38) of the damper (6) and the outer wall (26, 260) of the plate portion (24, 240) are cylindrical, and the coupling between the damper (6) and the plate portion (24, 240) is a cylindrical coupling.

13. A linear actuation device (1) according to claim 12, wherein the damper (6) further comprises an outer wall(42) , and at least one of said outer wall (42) and saidinner wall (38) has a concavity (43a, 43b) which extends circumferentially, preferably in the central portion of said outer wall (42) and / or said inner wall (38) , preferably said central portion being equidistant from the ends of said outer wall (42) and / or said inner wall (38) .

14. A linear actuation device (1) according to claim13, wherein said inner wall (38) and said outer wall (42) are connected to each other by an annular wall (40) perpendicular thereto, and the damper (6) has a front concavity (41a) facing the thrust plate (4, 4' ) and a rear concavity (41b) facing the threaded shaft (7) , each concavity (41a, 41b) being delimited by the inner wall (38) , the outer wall (42) and the annular wall (40) , preferably said annular wall (40) being equidistant from the ends of said inner wall (38) and said outer wall (42) .

15. A linear actuation device (1) according to claim 13 or 14, wherein the damper (6) comprises a plurality of axial channels (54) obtained in the outer wall (42) , preferably said axial channels (54) extend throughout the axial extension of the outer wall (42) of the damper, preferably the damper (6) comprising three equidistant axial channels (54) .

16. A linear actuation device (1) according to any one of the preceding claims, wherein the thrust plate (4, 4' ) and the joint element (5, 5' ) are made of metal material, preferably steel, or aluminum or alloys thereof, or other light alloys, and the damper (6) is made of rubber .

17. A linear actuation device (1) according to any one of the preceding claims, comprising a force sensor (46) configured to detect the braking force applied by the actuation device (1) , wherein the force sensor (46) is positioned behind the threaded shaft (7) .

18. A linear actuation device (1) according to any one of the preceding claims, comprising a spacer (47) coaxial with the threaded shaft (7) and an anti-rotation pin (21) , wherein the threaded shaft (7) is positioned passing through the spacer (47) , wherein the anti-rotation pin (21) is configured to allow a translation of the threaded shaft (7) in the axial direction and to prevent a rotation of the threaded shaft (7) about the axial direction, and wherein the spacer (47) is configured to transfer the clamping force from the nut screw (8) to the anti-rotation pin (21) .

19. A linear actuation device (1) according to claim18, comprising an axial bearing (48) coaxial with the threaded shaft (7) , wherein the threaded shaft (7) is positioned passing through the axial bearing (48) , wherein the axial bearing (48) is configured to ensure the rotation of the nut screw (8) and transmit the clamping force to the spacer ( 47 ) .

20. A linear actuation device (1) according to claim19, comprising a radial bearing (49) externally connected to the nut screw (8) and positioned adjacent to the axial bearing (48) on the side facing the thrust plate (4, 4' ) , wherein the radial bearing (49) is configured to support the radial stresses acting on the actuation device (1) .

21. A linear actuation device (1) according to any one of the preceding claims, comprising a cap (50) connected to the thrust plate (4, 4' ) and configured to make a fluid seal between the actuation device (1) and the pad (20) of the disc brake (2) , wherein the nut screw (8) defines a circumferential seat (51) interposed between an external toothing (12) of the nut screw (8) and the thrust plate (4, 4' ) , and the cap (50) is positioned in said circumferential seat (51) ,wherein, optionally, the thrust plate (4, 4' ) defines a circumferential groove (52) extending towards the inside of the thrust plate (4, 4' ) in the radial direction, and wherein the cap (50) is positioned in the circumferential seat (51) and one end of the cap (50) is inserted into the circumferential groove (52) .

22. A linear actuation device (1) according to claim 21, comprising an axial retaining ring (53) positioned externally to the nut screw (8) , wherein the axial retaining ring (53) is interposed between the cap (50) and an external toothing (12) of the nut screw (8) .

23. A disc brake (2) comprising a caliper (44) , comprising two mutually spaced apart side walls which delimit a disc space to accommodate a portion of a brake disc (45) , means for fixing the caliper to a vehicle, a connection structure which extends straddling the disc space and connects the side walls to each other, at least one pad seat formed in each of said side walls and adapted to accommodate at least one pad (20) , thrust means constrained to one or both side walls and adapted to bias the pads (20) against the brake disc (45) to clamp it, wherein the thrust means comprise the actuation device (1) according to any one of the preceding claims.

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