Disc brake caliper

Abstract

A disc brake caliper (1) is the object of the present invention, comprising a caliper body (2) arranged straddling a brake disc having a rotation axis defining an axial direction (A-A) and opposite friction surfaces, said caliper (1) comprising pads (3) accommodated in said caliper body (2) so as to slide substantially in an axial direction (A-A) with respect to the brake disc to act on said opposite friction surfaces respectively, said caliper (1) comprising a cylinder (4), forming a cylindrical wall (5) and a bottom wall (6) transverse to the cylindrical wall (5), said caliper (1) further comprising a parking braking system (10) comprising a rotating member (11); said rotating member (11) being rotatably accommodated inside a rotation seat (12) formed in the bottom wall (6) of the cylinder (4), so that the rotating member (11) is rotatable about a rotation axis substantially parallel to the axial direction (A-A), in which the cylinder (4) defines a first annular seat (13) and a second annular seat (14) made in the bottom wall (6), said first and second annular seats (13, 14) extending into the bottom wall (6) in the direction transverse to the axial direction (A-A) and leading into the rotation seat (12), said second annular seat (14) being different from said first annular seat (13), and being positioned in the opposite direction with respect to the inner surface (25) of the bottom wall (6) with respect to said first annular seat (13), in which the first annular seat (13) accommodates a first seal (15), and the second annular seat (14) accommodates a second seal (16), and in which the first and the second seals (15, 16) are configured so as to act between said rotating member (11) and said bottom wall (6) of the cylinder (4) to make a fluid seal; in which the first seal (15) comprises an O-ring (19) coupled to an anti-extrusion ring (20), in which said anti-extrusion ring (20) is interposed between the O-ring (19) and the rotating member (11), and it is made of less deformable material than the material of the O-ring (19); in which the bottom wall (6) of the cylinder (4) forms, at the first annular seat (13), at least a first backing step (27) which results in a concave polygon-shaped profile of the first annular seat (13) in a section parallel to the axial direction (A-A), in which said first backing step (27) comprises, in cross section, radially proximal portions and radially distal portions with respect to the rotation axis, in which said anti-extrusion ring (20) comprises an axial protrusion (28) inserted with shape coupling at the first backing step (27).

Description

DISC BRAKE CALIPERDESCRIPTIONField of the invention

[0001] The present invention relates to a disc brake caliper, in particular for a disc brake comprising an electromechanical parking brake.Background art

[0002] In recent years, the development of electromechanical parking brakes (EPBs) has focused on increasing the parking performance thereof, both in terms of the clamping force generated and service life.

[0003] In particular, current EPB devices are required to sustain at least 300,000 load cycles.

[0004] It has been observed that a correct fluid seal of the braking system plays a key role in increasing the service life of an EPB device, and thus the number of load cycles thereof.

[0005] Undesired brake fluid leakages and undesired air inlet from the outside cause EPB devices to deteriorate.

[0006] In fact, in the absence of a correct seal, the brake fluid can enter the gearmotor chamber of the EPB device and damage the working thereof, e.g., causing plastic gears to swell or the motor to short-circuit.

[0007] Additionally, due to the loss of the optimal seal, the consequent seeping of brake fluid generates a viciouscircle, further reducing the life of EPB devices.

[0008] To address said critical issues, current EPB devices are generally provided with a seal consisting of an 0- ring coupled to an anti-extrusion ring configured to prevent extrusion of the rubber of the 0-ring, which can be generated by the high brake fluid pressures.

[0009] Said known solution is not optimal because the resulting fluid seal greatly depends on the compression of the 0-ring within the seat in which it is accommodated.

[0010] Furthermore, since the 0-ring is mounted directly on the screw shaft of the EPB device, the relative sliding and heat generated during the movement of the screw cause significant wear and abrasion of the 0-ring. The wear of the 0-ring generates a significant reduction in the compression thereof, causing brake fluid leakages, reducing the life of the caliper.

[0011] A further problem caused by wear of the 0-ring and relative loss of compression thereof is the inlet of air during the actuation step of the brake without the presence of pressurized brake fluid.

[0012] In fact, actuation of the brake without the application of pressurized fluid causes the movement of the brake piston to generate negative pressure at the screw of the EPB.

[0013] In the presence of a worn sealing system, the negative pressure causes air to be sucked in from the outside, resulting in a spongy feel of the pedal, reducing the braking performance.

[0014] An attempt has been made to solve these critical issues and increase the seal of the system by placing multiple O-rings side by side.

[0015] However, placing multiple O-rings within the same seat has not been proven to be the solution because it does not solve the critical issues relating to the high brake fluid pressures, which act on the plurality of 0- rings, determining the seeping of brake fluid past the plurality of O-rings set side-by-side.

[0016] US2013037357A1 describes a disc brake caliper in which a two-stage seal is applied to a translating member of the service brake. One of the two sealing stages comprises a quadrangular section seal, configured to be compressed in the axial direction and easily deformable so as to provide the piston with a "roll-back" effect. Despite being suitable for application to a translating member, said known solution is not adapted to ensure a correct seal to a rotating member of a parking brake system because the rotation of the rotating member would exacerbate the deformation of the seal, which would then be unable to effectively prevent the seeping of brakefluid.

[0017] EP2273149A1 also describes a disc brake caliper, in which a dual-stage seal is applied to a service brake translating member (i.e. the piston). One of the two sealing stages comprises a seal configured to act initially integrally on the translating member. Said known solution is not applicable to a rotating member because adhesion to the rotating member would quickly damage the seal and the sealing ability thereof.

[0018] Moreover, EP4169783, to the applicant, shows a disc brake caliper, in which a two-stage seal is applied to a translating member of the service brake. One of the two sealing stages comprises a seal comprising a slider element and an O-Ring, in which said slider element would have the object of preventing wear of the O-Ring due to a rotatory rubbing thereof. However, it has been seen that said slider fails to completely fulfil said role and the O-ring is object of sudden wear. Solution

[0019] It is the object of the present invention to provide a disc brake caliper, comprising an improved parking- braking system and configured to solve at least some of the drawbacks of the prior art.

[0020] These and other objects are obtained by means of a disc brake caliper according to claim 1.

[0021] The dependent claims relate to preferred and advantageous embodiments of the present invention.Figures

[0022] In order to better understand the invention and appreciate the advantages thereof, a few non-limiting exemplary embodiments thereof will be described below with reference to the accompanying drawings, in which:

[0023] - figure 1 is a perspective view of a disc brake caliper along an axial section according to an embodiment of the invention;

[0024] - figure 2 is a side view of the disc brake caliper depicted in figure 1;

[0025] - figure 3 is a partially sectioned upper view of a disc brake caliper according to an embodiment of the invention;

[0026] - figure 4 is a detail view of a part of figure 3;

[0027] - figure 5 is a front view of an anti-extrusion ring comprised in a disc brake caliper according to an embodiment of the invention;

[0028] - figure 6 is a sectional view of the anti-extrusion ring in figure 5;

[0029] - figure 7 is a sectional view of a cylinder comprised in a disc brake caliper according to an embodiment of the invention;

[0030] - figure 8 is a view along the sectional plane V-Vindicated in figure 7;

[0031] - figure 9 shows an enlarged view of a detail in figure 7;

[0032] - figure 10 is a front view of a component of a brake disc caliper along an axial section according to an embodiment of the invention;

[0033] - figure 11 is a front view of a component of a brake disc caliper along an axial section according to a further embodiment of the invention;

[0034] - figure 12 is a front view of a component of a brake disc caliper along an axial section according to a further embodiment of the invention;

[0035] - figure 13 is a front view of a component of a brake disc caliper along an axial section according to a further embodiment of the invention;

[0036] - figure 14 is a front view of a component of a brake disc caliper along an axial section according to a further embodiment of the invention;

[0037] - figure 15 is a front view of a component of a brake disc caliper along an axial section according to a further embodiment of the invention;

[0038] - figure 16 is a front view of a component of a brake disc caliper, along an axial section, according to a further embodiment of the invention;

[0039] - figure 17 is a front view of a component of abrake disc caliper along an axial section according to a further embodiment of the invention.Description of some preferred embodiments

[0040] With reference to the figures, a disc brake caliper is generally indicated by reference numeral 1.

[0041] The disc brake caliper 1 comprises a caliper body 2 arranged straddling a brake disc having a rotation axis, which defines an axial direction A-A and opposite friction surfaces.

[0042] The caliper 1 comprises pads 3 accommodated in the caliper body 2 so it can slide substantially in an axial direction A-A with respect to the brake disc to act on the opposite friction surfaces, respectively.

[0043] Furthermore, the caliper 1 comprises a cylinder 4, which forms a cylindrical wall 5 and a bottom wall 6 transverse to the cylindrical wall 5.

[0044] The caliper 1 further comprises a piston 7, which forms a side wall 8 and a thrust wall 9 substantially transverse to the side wall 8 and opposite to the bottom wall 6 of the cylinder 4.

[0045] The bottom wall 6 forms an inner surface 25 facing the piston 7 and an opposite outer surface 26 facing opposite to the piston 7.

[0046] The piston 7 is accommodated inside the cylinder 4, and the side wall 8 of the piston 7 is adapted to slidewithin the cylindrical wall 5 of the cylinder 4.

[0047] The piston 7 is configured to be stressed by a pressurized brake fluid injectable into the cylinder 4, so as to bias at least one of the pads 3 against one of the brake disc friction surfaces, along a thrust direction substantially parallel to the axial direction A-A.

[0048] The caliper 1 further comprises a parking-braking system 10 which comprises a rotating member 11.

[0049] The rotating member 11 is rotatably accommodated inside a rotation seat 12 formed in the bottom wall 6 of the cylinder 4 so that the rotating member 11 is rotatable about a rotation axis substantially parallel to the axial direction A-A.

[0050] According to an aspect of the invention, the cylinder 4 defines a first annular seat 13 and a second annular seat 14 made in the bottom wall 6.

[0051] The first and second annular seats 13, 14 extend into the bottom wall 6 in a direction transverse to the axial direction A-A and lead into the rotation seat 12.

[0052] The second annular seat 14 is different to said first annular seat 13 and is positioned in a direction opposite to the inner surface 25 of the bottom wall 6 with respect to the first annular seat 13.

[0053] The first annular seat 13 accommodates a first seal15, and the second annular seat 14 accommodates a second seal 16.

[0054] The first and second seals 15, 16 are configured to act between the rotating member 11 and the bottom wall 6 of the cylinder 4 to create a fluid-tight seal.

[0055] Advantageously, the first and second seals 15, 16 provide an elevated seal and drastically reduce unwanted brake fluid leakage and air inlet from the outside.

[0056] Specifically, the first seal 15, closest to the pressurized brake fluid, shields the pressure and provides most of the seal. The second seal 16 allows stopping drops of brake fluid from seeping past the first seal 15, thus achieving an elevated seal.

[0057] According to an embodiment, the parking-braking system 10 comprises a screw-nut system formed by a screw 17 and a nut 18.

[0058] A translation of the nut 18 corresponds to a rotation of the screw 17, with respect to the caliper body 2, along a direction parallel to the axial direction A-A.

[0059] The nut 18 is configured to bias at least one of the pads 3 against one of said brake disc friction surfaces.

[0060] The rotating member 11 forms the screw 17.

[0061] Optionally, the screw-nut system defines a thread, and said thread is of the irreversible type.

[0062] Advantageously, said configuration drastically reduces the seeping of brake fluid past the screw 17, thus preserving the correct working of the additional components of the EPB device.

[0063] According to an embodiment, the first seal 15 comprises an O-ring 19 coupled to a sealing ring, which also has an anti-extrusion function and which will be called an anti-extrusion ring 20 hereafter.

[0064] The anti-extrusion ring 20 is interposed between the O-ring 19 and the rotating member 11 and is made of less deformable material than the material of the O-ring 19.

[0065] Optionally, the anti-extrusion ring 20 is made of a polymeric material, such as polytetrafluoroethylene (PTFE), or a polymeric material with PTFE filling in the polymer matrix.

[0066] Said anti-extrusion ring 20 being interposed between said O-ring 19 and the rotating member 11.

[0067] According to a preferred embodiment, the anti- extrusion ring 20 comprises an axial wall, extending parallel to the axial direction A-A, and it is interposed between said O-ring 19 and the rotating member 11.

[0068] The anti-extrusion ring 20 is coupled to the cylinder 4: i.e. the anti-extrusion ring 20 is engaged with the cylinder 4 thus being rotationally fixed.

[0069] In fact, the bottom wall 6 of the cylinder 4 formsat the first annular seat 13, at least a first backing step 27, which results in a concave polygon-shaped profile of the first annular seat 13, in a section parallel to the axial direction A-A, and said first anti- extrusion ring 20 comprises an axial protrusion 28 inserted with shape coupling into the first backing step 27.

[0070] According to an embodiment, the axial protrusion 28, in the cross-section, has a complementary shape with respect to that of the first backing step 27.

[0071] The first backing step 27, in cross-section, comprises radially proximal portions and radially distal portions with respect to the axial direction A-A, and the axial protrusion 28 of the first backing step 27 has a complementary shape. A circumscribed imaginary circumference or an imaginary circumference inscribed within the regular polygon preferably has the center on the rotation axis.

[0072] According to a preferred embodiment, the first backing step 27, in the cross-section, has a regular polygon shape. Complementarily, the axial protrusion 28, in the cross-section, has said regular polygon shape. The imaginary circumference circumscribed around the regular polygon preferably has the center on the rotation axis.

[0073] According to a preferred embodiment, the firstbacking step 27, in the cross-section, has an irregular polygon shape. Complementarily, the axial protrusion 28, in the cross-section, has said irregular polygon shape.

[0074] According to a preferred embodiment, the first backing step 27, in the cross-section, has an ellipse shape. Complementarily, the axial protrusion 28, in the cross-section, has said ellipse polygon shape. Preferably, said ellipse is concentric to the rotation axis.

[0075] According to a preferred embodiment, the first backing step 27, in the cross-section, has a circumference shape, which is offset with respect to the rotation axis. Complementarily, the axial protrusion 28, in the cross-section, has said circumference shape, which is offset with respect to the rotation axis.

[0076] According to an embodiment, the backing step 27 extends into the bottom wall 6 in the axial direction towards the outer surface 26, i.e., distally from the inner surface 25.

[0077] Advantageously, said configuration of the first seal 15 prevents relative rotations between the 0-ring 19 and the screw 17, in particular preventing relative rotations between the anti-extrusion ring 20 and the screw 17. Thereby, it is certain that the O-ring 19 works subjected to static and not dynamic conditions, allowing asignificant reduction in cross-sectional (or chord) wear of the O-ring.

[0078] Advantageously, the anti-extrusion ring 20 is mechanically rotationally locked, resulting fixed in any operating state.

[0079] According to an embodiment, the second seal 16 is a scraper.

[0080] Advantageously, a scraper ensures an elevated seal against the seeping of brake fluid, the inlet of dust, rust, or air leaks from outside, achieving a high fluid seal in synergy with the first seal 15.

[0081] More advantageously, the scraper makes up for any wear, and the consequent reduction in the seal of the anti-extrusion ring 20 of the first seal 15, thereby continuing to preserve the seal of the entire braking system.

[0082] According to an embodiment, the second seal 16 is:

[0083] - an O-ring; or

[0084] - an X-ring; or

[0085] - a symmetrical or asymmetrical lip seal; or

[0086] - a symmetrical or asymmetrical lip seal, incorporating a reinforcing insert 23, made of a metal or polymeric material; or

[0087] - a lip seal defining three lobes 21 in a section parallel to the axial direction A-A; or

[0088] - a lip seal defining four lobes 21 in a section parallel to the axial direction A-A.

[0089] Advantageously, the scrapers thus configured make up for any deviations in geometric tolerances, due to temperature variations, for example, to preserve a correct sealing of the braking system.

[0090] According to an embodiment, the second seal 16 is a lip seal defining a three-lobe profile 21 in a section parallel to the axial direction A-A.

[0091] Two of the three lobes 21 are biased against the rotating member 11 and one of the three lobes 21 is biased against the bottom wall 6 of the cylinder 5.

[0092] Optionally, two of the three lobes 21 are pinned against the rotating member 11 opposite to each other along a direction parallel to the axial direction A-A.

[0093] Optionally, one of the three lobes 21 biased against the bottom wall 6 of the cylinder 5 is pinned against said bottom wall 6 in the direction of the inner surface 25 of the bottom wall 6.

[0094] Optionally, the second seal 16 is a lip seal, which defines a four-lobe profile 21 in a section parallel to the axial direction A-A, and in which two of the four lobes 21 are biased against the rotating member 11 and two opposite lobes 21 are biased against the bottom wall6 of the cylinder 5.

[0095] Optionally, two of the four lobes 21 are pinned against the rotating member 11 opposite to each other along a direction parallel to the axial direction A-A, and two opposite lobes 21 are pinned against the bottom wall 6 opposite to each other along a direction parallel to the axial direction A-A.

[0096] According to an embodiment, the second seal 16 comprises a seal body 22 made of a polymeric material, and a reinforcing insert 23, preferably made of metal, incorporated within the seal body 22.

[0097] The reinforcing insert 23 is configured to promote the gripping of the second seal 16 to the bottom wall 6.

[0098] Optionally, the second seal 16 defines a three-lobe profile 21 in a section parallel to the axial direction A-A, and wherein one of the three lobes 21 is biased against the bottom wall 6 of the cylinder 5, and wherein the reinforcing insert 23 is incorporated in said lobe 21.

[0099] Advantageously, the reinforcing insert 23 is configured to prevent the elastic deformation of said lobe 21.

[0100] According to an embodiment, the second annular seat 14 defines a concave polygon-shaped profile in a section parallel to the axial direction A-A.

[0101] Optionally, said concave polygon has at leastone concave angle of about 270°.

[0102] Optionally, the second seal 16 accommodated by the second annular seat 14 is an asymmetrical lip seal.

[0103] According to an embodiment, the bottom wall 6 of the cylinder 4 forms, at the second annular seat 14, at least a second backing step 24, which, in a section parallel to the axial direction A-A, determines said concave polygon-shaped profile of the second annular seat 14.

[0104] The second seal 16 defines a three-lobe 21 or four-lobe 21 profile in a section parallel to the axial direction A-A.

[0105] At least one lobe 21 of the second seal 16 is positioned to abut against said at least a second backing step 24.

[0106] According to an embodiment, between the first annular seat 13 and the second annular seat 14, along a section parallel to the axial direction A-A, the bottom wall 6 of the cylinder 4 defines a distance D comprised between:

[0107] - 2.0 mm and 6.0 mm; or

[0108] - 2.4 mm and 5.2 mm; or

[0109] - 2.9 mm and 3.8 mm.

[0110] Advantageously, said distance D strengthens the inner surface 25 of the bottom wall 6, which is biased bythe pressure of the brake fluid.

[0111] According to an embodiment, the first annular seat 13 leads into said inner surface 25 of the bottom wall 6.

[0112] Optionally, the second annular seat 14 leads into said outer surface 26 of the bottom wall 6.

[0113] Advantageously, when it leads into the outer surface 26 and is free from a second backing step 24, a seal incorporating a reinforcing insert 23 can be inserted into the second annular seat 14.

[0114] Optionally, between the first annular seat 13 and said inner surface 25, along a section parallel to the axial direction A-A, the bottom wall 6 defines a first distance LI comprised between:

[0115] - 0.5 mm and 4.0 mm; or

[0116] - 1.0 mm and 3.0 mm; or

[0117] equal to 2.8 mm.

[0118] Optionally, between the second annular seat 14 and said outer surface 26, along a section parallel to the axial direction A-A, the bottom wall 6 defines a second distance L2 comprised between:

[0119] - 0.5 mm and 4.0 mm; or

[0120] - 1.0 mm and 3.0 mm; or

[0121] equal to 2.3 mm; or

[0122] equal to 2.5 mm.

[0123] Optionally, along a section parallel to the axial direction A-A, the first annular seat 13 has a length comprised between:

[0124] - 3.0 mm and 4.0 mm; or

[0125] equal to 3.6 mm.

[0126] Optionally, along a section parallel to the axial direction A-A, the second annular seat 14 has a length comprised between:

[0127] - 2.5 mm and 5.0 mm; or

[0128] equal to 3.1 mm; or

[0129] equal to 3.9 mm; or

[0130] equal to 4.7 mm.

[0131] Optionally, along a section transverse to the axial direction A-A, the first annular seat 13 defines a first diameter DI with respect to the rotation axis of the rotating member 11 comprised between:

[0132] - 18.0 mm and 21.0 mm; or

[0133] equal to 19.6 mm.

[0134] Optionally, in which embodiment, in which the backing step 27 has a circumference shape and defines a protrusion diameter Ds comprised between:

[0135] - 15.0 mm and 18.5 mm; or

[0136] equal to 17.0 mm.

[0137] Said circumference is offset with respect to the rotation axis, defining an offset E comprisedbetween:

[0138] - 0.50 mm and 2.0 mm; or

[0139] equal to 1.0 mm.

[0140] Optionally, along a section transverse to the axial direction A-A, the second annular seat 14 defines a second diameter D2 with respect to the rotation axis of the rotating member 11 comprised between:

[0141] - 16.0 mm and 20.0 mm; or

[0142] equal to 16.6 mm; or

[0143] equal to 18.6 mm;

[0144] equal to 19.6 mm.

[0145] Optionally, at the second annular seat 14, the bottom wall 6 of the cylinder 4 forms at least a second backing step 24, which defines, along a section transverse to the axial direction A-A, a third diameter D3 with respect to the rotation axis of the rotating member 11 comprised between:

[0146] - 15.0 mm and 18.0 mm; or

[0147] - 16.0 mm and 17.0 mm; or

[0148] equal to 16.6 mm.

[0149] Optionally, along a section parallel to the axial direction A-A, the bottom wall 6 of the cylinder 4 defines a thickness W between the inner surface 25 and the outer surface 26 comprised between:

[0150] - 12.0 mm and 14.0 mm; or

[0151] equal to 13.5 mm.

[0152] Optionally, the first step 27, preferably inside the first seat 13, defines, along a section parallel to the axial direction A-A, a step length Lg comprised between:

[0153] - 0.5 mm and 2.0 mm; or

[0154] equal to 1.0 mm.

[0155] Obviously, those skilled in the art will be able to make changes or adaptations to the present invention, without, however, departing from the scope of the following claims.LIST OF REFERENCESI. Caliper2. Caliper body3. Pads4. Cylinder5. Cylindrical wall6. Bottom wall7. Piston8. Side wall9. Thrust wall10. Parking-braking systemII. Rotating member12. Rotation seat13. First annular seat14. Second annular seat15. First seal16. Second seal17. Screw18. Nut screw19. O-ring20. Anti-extrusion ring21. Lobes22. Seal body23. Reinforcing insert24. Second backing step25. Inner wall26. Outer wall27. First backing step28. Axial Protrusion A-A. Axial directionD. DistanceDI. First diameterD2. Second diameterD3. Third diameter Ds. Protrusion diameterE. OffsetLI. First lengthL2. Second lengthLg. Step length W. Thickness

Claims

CLAIMS1. A disc brake caliper (1) comprising a caliper body (2) arranged straddling a brake disc having a rotation axis defining an axial direction (A-A) and opposite friction surfaces, said caliper (1) comprising pads (3) accommodated in said caliper body (2) so as to slide substantially in an axial direction (A-A) with respect to the brake disc to act on said opposite friction surfaces, respectively, said caliper (1) comprising:- a cylinder (4), forming a cylindrical wall (5) and a bottom wall (6) transverse to the cylindrical wall (5);- a piston (7), forming a side wall (8) and a thrust wall (9) substantially transverse to the side wall (8) and opposite to the bottom wall (6) of the cylinder (4); wherein said bottom wall (6) forms an inner surface (25) facing the piston (7) and an opposite outer surface (26) facing away from the piston (7); wherein the piston (7) is accommodated inside the cylinder (4), and the side wall (8) of the piston (7) is adapted to slide within the cylindrical wall (5) of the cylinder (4); wherein the piston (7) is configured to be biased by a pressurized brake fluid injectable into the cylinder (4), so as to bias at least one of said pads (3) against oneof said friction surfaces of the brake disc, along a thrust direction substantially parallel to the axial direction (A-A); said caliper (1) further comprising a parking-braking system (10) which comprises a rotating member (11); said rotating member (11) being rotatably accommodated inside a rotation seat (12) formed in the bottom wall (6) of the cylinder (4) so that the rotating member (11) is rotatable about a rotation axis substantially parallel to the axial direction (A-A); wherein the cylinder (4) defines a first annular seat (13) and a second annular seat (14) obtained in the bottom wall (6), said first and second annular seats (13, 14) extending into the bottom wall (6) in a direction transverse to the axial direction (A-A) and leading into the rotation seat(12), said second annular seat (14) being distinct from said first annular seat (13), and being positioned in a direction opposite to the inner surface (25) of the bottom wall (6) with respect to said first annular seat(13), wherein the first annular seat (13) accommodates a first seal (15), and the second annular seat (14) accommodates a second seal (16)and wherein the first and second seals (15, 16) are configured to act between said rotating member (11) and said bottom wall (6) of the cylinder (4) to obtain a fluid seal; wherein the first seal (15) comprises an 0-ring (19) coupled to a anti-extrusion ring (20), wherein said anti-extrusion ring (20) is made of less deformable material than the material of the O-ring (19); wherein the caliper (1) is characterized in that the bottom wall (6) of the cylinder (4) forms, at the first annular seat (13), at least a first backing step (27) which results in a concave polygon-shaped profile of the second annular seat (13) in a section parallel to the axial direction (A-A), wherein said first backing step (27) comprises, in cross section, radially proximal portions and radially distal portions with respect to the rotation axis, wherein said anti-extrusion ring (20) comprises an axial protrusion (28) inserted with shape coupling into the first backing step (27).

2. A caliper (1) according to claim 1, wherein the parking-braking system (10) comprises a screw-nut system formed by a screw (17) and a nut (18), wherein a rotation of the screw (17) corresponds to a translation of the nut (18), with respect to the caliper body (2), along a direction parallel to the axialdirection (A-A), said nut (18) being configured to bias at least one of said pads (3) against one of said friction surfaces of the brake disc, and wherein the rotating member (11) forms said screw (17), and wherein, optionally, the screw-nut system defines a thread, and said thread is of the irreversible type.

3. A caliper (1) according to claim 1 or 2, wherein the first backing step (27), in cross section, is shaped like a regular polygon, or an irregular polygon, or an ellipse, or an offset circumference with respect to the rotation axis, wherein the axial protrusion (28), in cross section, has a shape complementary to that of the first backing step (27).

4. A caliper (1) according to any one of the preceding claims, wherein the backing step (27) extends into the bottom wall (6) in the axial direction towards the outer surface (26), i.e., distally from the inner surface (25).

5. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) is a scraper.

6. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) is:- an O-ring; or- an X-ring; or- a symmetrical or asymmetrical lip seal; or- a symmetrical or asymmetrical lip seal embedding a reinforcing insert (23), preferably made of metal; or- a lip seal defining three lobes (21) in a section parallel to the axial direction (A-A); or- a lip seal defining four lobes (21) in a section parallel to the axial direction (A-A).

7. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) is a lip seal, which defines a three-lobe profile (21) in a section parallel to the axial direction (A-A), and wherein two of the three lobes (21) are biased against the rotating member (11) and one of the three lobes (21) is biased against the bottom wall (6) of the cylinder (4), and / or wherein two of the three lobes (21) are pinned against the rotating member (11), opposite to each other along a direction parallel to the axial direction (A-A), and / or wherein one of the three lobes (21) biased against the bottom wall (6) of the cylinder (4) is pinned against said bottom wall (6) towards the inner surface (25) of the bottom wall (6), and / or wherein the second seal (16) is a lip seal, which defines a four-lobe profile (21) in a section parallel to the axial direction (A-A),and wherein two of the four lobes (21) are biased against the rotating member (11) and two opposite lobes (21) are biased against the bottom wall (6) of the cylinder (4), and / or wherein two of the four lobes (21) are pinned against the rotating member (11) opposite to each other along a direction parallel to the axial direction (A-A), and two opposite lobes (21) are pinned against the bottom wall (6) opposite to each other along a direction parallel to the axial direction (A-A).

8. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) comprises a seal body (22) made of a polymer material, and a reinforcing insert (23) incorporated inside the seal body (22), wherein the reinforcing insert (23) is configured to promote the gripping of the second seal (16) to the bottom wall (6), wherein, optionally, the second seal (16) defines a three-lobe profile (21) in a section parallel to the axial direction (A-A), and wherein one of the three lobes (21) is biased against the bottom wall (6) of the cylinder (4), and wherein the reinforcing insert (23) is incorporated inside said lobe (21), and wherein, optionally, the reinforcing insert (23) is configured to prevent the elastic deformation of said lobe (21).

9. A caliper (1) according to any one of the preceding claims, wherein the second annular seat (14) defines a concave polygon-shaped profile in a section parallel to the axial direction (A-A), wherein, optionally, said concave polygon has at least one concave angle of about 270°, and wherein, optionally, the second seal (16) accommodated by the second annular seat (14) is an asymmetrical lip seal.

10. A caliper (1) according to claim 9, wherein the bottom wall (6) of the cylinder (4) forms, at the second annular seat (14), at least one second backing step (24) which results in said concave polygon-shaped profile of the second annular seat (14) in a section parallel to the axial direction (A-A), wherein the second seal (16) defines a three-lobe (21) or four-lobe (21) profile in the section parallel to the axial direction (A-A), and wherein at least one lobe (21) of the second seal (16) is positioned to abut against said at least one second backing step (24).

11. A caliper (1) according to any one of the preceding claims, wherein between the first annular seat (13) and the second annular seat (14), along a section parallel to the axial direction (A-A), the bottom wall (6) of thecylinder (4) defines a distance (D) of between:- 2.0 mm and 6.0 mm; or- 2.4 mm and 5.2 mm; or- 2.9 mm and 3.8 mm.

12. A caliper (1) according to any one of the preceding claims, wherein the first annular seat (13) leads into said inner surface (25) of the bottom wall (6); and / or wherein the second annular seat (14) leads into said outer surface (26) of the bottom wall (6); and / or wherein, between the first annular seat (13) and said inner surface (25), along a section parallel to the axial direction (A-A), the bottom wall (6) defines a first distance (LI) of between:- 0.5 mm and 4.0 mm; or- 1.0 mm and 3.0 mm; or equal to 2.8 mm, and / or wherein between the second annular seat (14) and said outer surface (26), along a section parallel to the axial direction (A-A), the bottom wall (6) defines a second distance (L2) of between:- 0.5 mm and 4.0 mm; or- 1.0 mm and 3.0 mm; or equal to 2.3 mm; or equal to 2.5 mm, and / or wherein, along a section parallel to the axialdirection (A-A), the first annular seat (13) has a length of between:- 3.0 mm and 4.0 mm; or equal to 3.6 mm, and / or wherein, along a section parallel to the axial direction (A-A), the second annular seat (14) has a length of between:- 2.5 mm and 5.0 mm; or equal to 3.1 mm; or equal to 3.9 mm; or equal to 4.7 mm, and / or wherein, along a section transverse to the axial direction (A-A), the first annular seat (13) defines a first diameter (D1) with respect to the rotation axis of the rotating member (11) of between:- 18.0 mm and 21.0 mm; or equal to 19.6 mm, and / or wherein, along a section transverse to the axial direction (A-A), the second annular seat (14) defines a second diameter (D2) with respect to the rotation axis of the rotating member (11) of between:- 16.0 mm and 20.0 mm; or equal to 16.6 mm; or equal to 18.6 mm; equal to 19.6 mmand / or wherein, at the second annular seat (14), the bottom wall (6) of the cylinder (4) forms at least one second backing step (24) which defines, along a section transverse to the axial direction (A-A), a third diameter (D3) with respect to the rotation axis of the rotating member (11) of between:- 15.0 mm and 18.0 mm; or- 16.0 mm and 17.0 mm; or equal to 16.6 mm; and / or wherein, along a section parallel to the axial direction (A-A), the bottom wall (6) of the cylinder (4) defines a thickness (W) between the inner surface (25) and the outer surface (26) of between:- 12.0 mm and 14.0 mm; or equal to 13.5 mm.

13. A caliper (1) according to any one of the preceding claims, wherein the backing step (27) is in the shape of a circumference and defines a protrusion diameter (Ds) of between:- 15.0 mm and 18.5.0 mm; or equal to 17.0 mm; and said circumference is offset with respect to the rotation axis, defining an offset (E) of between:- 0.5 mm and 2.0 mm; or equal to 1.0 mm.

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