Brake caliper piston and brake caliper

Abstract

The invention relates to a piston (10) for a brake caliper (1), comprising a side wall (11) extending predominantly in an axial direction (A-A) between a first annular edge (12) configured to be in contact with a first brake pad (4) and a second annular edge (13) configured to receive a thrust force from a brake fluid, and a spacer (14) disposed between the first annular edge (12) and the second annular edge (13). The spacer (14) extends at least in a radial direction (R-R), the radial direction (R-R) being transverse to the axial direction (A-A), the spacer (14) comprising a second brake fluid side surface (16) and a first pad side surface (15) adapted to face the first brake pad (4), the side wall (11) and the spacer (14) delimiting a thrust seat (18) and a ventilation chamber (17), the thrust seat (18) and the ventilation chamber (17) being spaced apart from each other. The thrust seat (18) and the ventilation chamber (17) are fluidically separated in the axial direction (A-A) by the spacer (14), the thrust seat (18) being open at the second annular edge (13) and closed at the second brake fluid side surface (16), and the thrust seat (18) being open at the second annular edge (13) and closed at the second brake fluid side surface (16). The thrust seat (18) is adapted to at least partially receive a thrust means (19) for mechanically actuating the piston (10), followed by biasing the first brake pad (4), in which the ventilation chamber (17) is open at the first annular edge (12) and is closed at least by the first pad side surface (15), and in which the ventilation chamber (17) is closed at least by the first pad side surface (15), the thrust seat (18) is adapted to at least partially receive a thrust means (19) for mechanically actuating the piston (10), followed by biasing the first brake pad (4). The side wall (11) comprises a first side wall part (20) with a first outer diameter (De1) and a second side wall part (21) with a second outer diameter (De2), the first outer diameter (De1) is larger than the second outer diameter (De2), the first side wall part (20) internally delimits at least the ventilation chamber (17), and the second side wall part (21) internally delimits at least the ventilation chamber (17). The piston (10) comprises a first side wall part (20) and a second side wall part (21), the second side wall part (21) internally at least partially delimits the thrust seat (18), the piston (10) comprises a third annular edge (22) extending predominantly in the radial direction (R-R), the third annular edge (22) externally connects the first side wall part (20) and the second side wall part (21) in an undercut manner, and the third annular edge (22) comprises a second annular edge (22) extending predominantly in the radial direction (R-R). The actuator is coupled to the brake fluid to receive thrust from the brake fluid.

Description

Technical Field

[0001] The invention relates to a piston for a brake caliper and a brake caliper. Background Art

[0002] Brake calipers are known which comprise at least one piston which can be actuated both by brake fluid acting on brake pads as a service brake and by a mechanically or electrically actuated thrust member acting on the brake pads as a parking brake, for example an electromechanical parking brake (EPB).

[0003] This brake caliper comprises a caliper body in which a hollow cylinder is formed which is bounded by a cylindrical wall and a bottom wall substantially transverse to the cylindrical wall. The bottom wall delimits internally a through-seating portion which is adapted to accommodate in a sealed and rotating manner at least a portion of a rotating member which can be connected on one side to an actuating mechanism, such as an electric motor, and on the other side to a thrust member connectable to a piston. The piston comprises a thrust head adapted to contact a brake pad and a side wall adapted to slide in a sealed manner relative to the cylindrical wall. Furthermore, the piston delimits, by the thrust head and the side wall, an open cavity on the opposite side of the thrust head, which is adapted to at least partially accommodate a thrust member coupled to a rotating member of a parking brake device. The thrust member is coupled to the rotating member to convert the rotation of the rotating member into a translation of the thrust member, thereby allowing a displacement in an axial direction, which then biases the brake pad.

[0004] In this type of brake caliper, brake fluid is introduced between the bottom wall of the cylinder and the piston in a fluid-tight manner, allowing the piston to be actuated by means of fluid pressure, wherein the rotating member and the thrust member are immersed in the brake fluid and allowing the piston to be actuated as a parking brake without considering the effect of the fluid.

[0005] When the brake caliper is operated as a service brake, the interaction between the brake pad and the brake disc generates heat, which reaches a high temperature of about several hundred degrees. This heat is transferred to the caliper body and the piston, thereby increasing the temperature of the brake fluid.

[0006] As is known, in the brake calipers of disc brakes, when the brake fluid becomes overheated and approaches the boiling point, gas bubbles are generated in the brake system. Unlike the essentially incompressible brake fluid, these gas bubbles lead to an increase in the travel of the brake actuation device, such as a pedal or a lever, to compress these bubbles during the braking action, thus affecting the braking comfort and possibly the braking action itself.

[0007] In addition to such problems, in such brake calipers, excessive increases in the temperature of the brake fluid can also cause various components of the thrust member and the rotating member immersed in the brake fluid to expand and subsequently contract during cooling. It has been found that the heating and cooling cycles and the resulting expansion and contraction of the components of the parking system immersed in the brake fluid in the cylinder chamber can cause the operation of the parking brake to be impaired until the brake caliper cools down.

[0008] Furthermore, after repeated application of the service brakes on a vehicle on an incline, overheating of the brake fluid increases the risk of reliability of the parking brake when it is applied. In fact, since the discs, pads, as well as the thrust and rotating members are immersed in the brake fluid, they expand due to the increase in temperature and then reduce in size when they cool down, resulting in the parking force initially built up on the hot disc being insufficient to keep the vehicle stationary on the incline after the caliper has cooled down.

[0009] Therefore, a strong need is felt for designing a solution for brake calipers that allows overheating of the brake fluid to be avoided.

[0010] Furthermore, among the needs felt in this field is the need to make a disc brake caliper that is as light as possible, in order to limit as much as possible the unsprung masses of the vehicle associated with the disc brake, and on the other hand it is necessary to ensure that the caliper body has the necessary rigidity to prevent it from deforming when in use and affecting the braking action. In particular, any deformation of the caliper body could affect its sliding relative to the support and there would therefore be an incorrect distribution of the thrust acting on the pad and thus on the opposite face of the brake band. Obviously, this need for rigidity and lightweighting is mutually contradictory, since increasing the rigidity is usually achieved by increasing the thickness of the part and the associated mass. Summary of the invention

[0011] The object of the present invention is to provide a brake piston and a brake caliper which allow better resistance to increases in the temperature of the brake fluid than currently known brake pistons and brake calipers.

[0012] Another object of the present invention is to provide a piston and a brake caliper capable of obtaining a high resistance to increases in the temperature of the brake fluid by limiting the space available for the brake fluid in the caliper body, i.e., by limiting the size of the pressure chamber defined between the piston and the cylinder formed in the caliper body, thereby reducing the weight of the brake caliper and maintaining a high stress resistance.

[0013] These and other objects are achieved by a piston according to claim 1 and a brake calliper according to claim 8 .

[0014] The dependent claims relate to preferred and advantageous embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to better understand the present invention and appreciate the advantages of the present invention, some non-limiting exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0016] - Figure 1 is an axonometric view of a brake caliper for a disc brake according to an embodiment of the present invention;

[0017] - Figure 2 yes Figure 1 A side view of the brake caliper shown in;

[0018] - Figure 3 is a side view of a brake caliper according to an embodiment of the invention, cut along a plane including the axial direction AA and the radial direction RR, wherein a piston and a thrust device that can be actuated by a brake fluid for braking the vehicle as a service brake and a parking brake can be seen, wherein the piston delimits a ventilation chamber in the direction of a first brake pad, thereby allowing a septum of the piston to be thermally isolated, the septum separating the ventilation chamber from a thrust seat delimited by the piston, in which the thrust device immersed in the brake fluid can be accommodated, wherein a stepped piston side wall can also be seen, thereby allowing the radial size of the pressure chamber into which the brake fluid is introduced to be reduced by moving the brake fluid away from the first brake pad;

[0019] - Figure 4 is an isometric view of a piston according to the invention, which can be inserted in a sliding manner into a Figure 3 a cylinder delimited by a brake caliper in which a ventilation chamber delimited by a piston can be seen;

[0020] - Figure 5 According to an embodiment of the present invention Figure 4 An exploded isometric view of a piston and a thrust device, which can be accommodated in a thrust seat delimited by the piston and is configured to actuate the piston mechanically and / or electromechanically;

[0021] - Figure 6 is an axonometric view of a piston according to the present invention, cut along a plane including an axial direction AA and a radial direction RR according to an embodiment of the present invention;

[0022] - Figure 7is a front view of a piston according to the invention, wherein a first surface of the spacer facing the brake pad can be seen, which first surface delimits the bottom of the pressure chamber and, according to an embodiment, has a convex central portion and two concave peripheral portions;

[0023] - Figure 8 is a front view of a piston according to the invention, wherein a first surface of the spacer facing the brake pad can be seen, which first surface delimits the bottom of the pressure chamber and, according to an embodiment, has a convex circular central portion and a concave peripheral annular crown portion. DETAILED DESCRIPTION

[0024] According to a general embodiment, a piston for a brake caliper 1 is denoted by reference numeral 10 .

[0025] The piston 10 comprises a side wall 11 extending mainly in the axial direction AA. The piston 10 comprises a first annular edge configured to contact the first brake pad 4. The piston 10 comprises a second annular edge 13 configured to receive a thrust from the brake fluid. The side wall 11 extends between the first annular edge 12 and the second annular edge 13.

[0026] The piston 10 comprises a spacing portion 14 extending at least in a radial direction RR, wherein the radial direction RR is transverse to the axial direction AA.

[0027] The spacer 14 includes a first pad side surface 15 adapted to face the first brake pad 4. The spacer 14 includes a second brake fluid side surface 16 adapted to face the opposite side of the first pad side surface 15 in the axial direction AA.

[0028] The side wall 11 and the partition 14 delimit a thrust seat 18 and a plenum chamber 17 , wherein the thrust seat 18 and the plenum chamber 17 are fluidically separated in the axial direction AA by the partition 14 .

[0029] The thrust seat 18 is open at the second annular edge 13 and is closed at the second brake fluid side surface 16 .

[0030] The thrust seat 18 is adapted to at least partially receive a thrust device 19 to mechanically actuate the piston 10 and, in turn, bias the first brake pad 4 .

[0031] The ventilation chamber 17 is open at the first annular edge 12 and is closed at least by the first pad side surface 15 .

[0032] Advantageously, said ventilation chamber 17 is suitable for containing air to thermally insulate the spacer 14. Air can thus be trapped between the pad and the spacer 14, thereby reducing the heat transfer from the pad area to the thrust seat 18 in which the brake fluid is present when the piston is in the operating state in the brake caliper 1.

[0033] Advantageously, the side wall 11 comprises a first side wall portion 20 having a first outer diameter De1 and a second side wall portion 21 having a second outer diameter De2, wherein the first outer diameter De1 is greater than the second outer diameter De2. The first side wall portion 20 internally delimits at least the ventilation chamber 17. The second side wall portion 21 at least partially internally delimits the thrust seat 18.

[0034] The piston 10 comprises a third annular edge 22 extending mainly in the radial direction RR, wherein the third annular edge 22 externally connects the first side wall portion 20 and the second side wall portion 21 in an undercut manner to receive the thrust from the brake fluid. In other words, the third annular edge 22 forms a shoulder of the side wall 11 extending in the radial direction.

[0035] According to an embodiment, the partition 14 comprises, on one side of the first pad side surface 15, a central portion 23 and a peripheral portion 24, wherein the central portion 23 is convex relative to the peripheral portion 24. According to an embodiment, the peripheral portion 24 is concave relative to the central portion 23. This allows to ensure that the air is retained in the ventilation chamber. Furthermore, the geometry of the central portion 23 and the peripheral portion 24 allows to increase the turbulent movement of the air present in the ventilation chamber when the air enters the ventilation chamber, thus avoiding excessive overheating of the partition 14.

[0036] According to an embodiment, the central portion 23 has a circular shape, and the peripheral portion 24 has an annular crown shape surrounding the central portion 23. According to an embodiment, the central portion 23 is bone-shaped, and the peripheral portion 24 is formed by two crescent-shaped portions separated by the central portion 23.

[0037] According to an embodiment, the first annular edge 12 includes at least one contact tooth 25 and at least one recess 26, wherein the at least one contact tooth 25 is raised relative to the at least one recess 26 along the axial direction AA or in a direction parallel to the axial direction AA, so that when the at least one tooth 25 is in contact with the first brake pad 4, the recess 26 forms a radial window with the side wall 11, and the radial window is suitable for allowing air to enter and exit the ventilation chamber 17 and reducing the contact surface between the first annular edge 12 and the first brake pad 4.

[0038] According to an embodiment, the first annular edge 12 includes a plurality of the at least one contact toothed portion 25 and a plurality of the at least one recessed portion 26 alternately arranged along the circumference of the first annular edge 12 .

[0039] According to an embodiment, the first side wall portion 20 comprises a first tubular portion 27. According to a first embodiment, the first tubular portion 27 has a first thickness S1 and a first axial length A1. According to an embodiment, the first tubular portion 27 delimits the ventilation chamber 17 internally.

[0040] According to an embodiment, the second side wall portion 21 comprises a second tubular portion 28 connected to the first tubular portion 27. According to an embodiment, the second tubular portion 28 has a second thickness S2 and a second axial length A2. According to an embodiment, the second tubular portion 28 at least partially delimits the thrust seat 18.

[0041] According to an embodiment, the first axial length A1 is at least equal to the second axial length A2.

[0042] According to an embodiment, the first thickness S1 is at least equal to the second thickness S2. According to an embodiment, the second thickness S2 is smaller than the first thickness S1.

[0043] According to an embodiment, the first side wall portion 20 comprises a third tubular portion 29 interposed between the first tubular portion 27 and the second tubular portion 29. According to an embodiment, the third tubular portion 29 is connected to the second tubular portion 28 via the third annular edge 22.

[0044] According to the first embodiment, the third tubular portion 29 has a third thickness S3 and a third axial length A3.

[0045] According to an embodiment, the third thickness S3 is at least twice the first thickness S1.

[0046] According to an embodiment, the third axial length A3 is at least twice the first thickness S1 .

[0047] According to an embodiment, the first axial length A1 is greater than the third axial length A3.

[0048] According to an embodiment, the first tubular portion 27 and the spacer 14 form a cup-shaped portion.

[0049] According to an embodiment, the second tubular portion 28 and the third tubular portion 29 and the spacer 14 form a T-shaped portion. According to an embodiment, the third tubular portion 29 forms a limited handle of the T-shaped portion, and the third tubular portion 29 connected to the spacer 14 forms a head of the T-shaped portion.

[0050] Advantageously, providing that the thickness of the third tubular portion 29 is greater than the thickness of the first tubular portion and the thickness of the second tubular portion and providing that the length of the third tubular portion 29 is equal to at least half the outer diameter of the first wall portion 20 allows to mitigate overheating and heat transfer from the pad side to the third annular edge 22 facing the brake fluid.

[0051] According to an embodiment, the first pad side surface 15 and the second brake fluid side surface 16 are diametrically opposite to each other along the axial direction AA.

[0052] According to an embodiment, said first pad side surface 15 and said second brake fluid side surface 16 comprise respective central portions extending mainly in a direction parallel to said radial direction RR.

[0053] According to an embodiment, said first annular edge 12 and said second annular edge 13 extend mainly in a direction parallel to said radial direction RR and form opposite axial ends of said piston 10 .

[0054] According to an embodiment, said first annular edge 12 and said second annular edge 13 extend mainly along a respective circumferential direction CC being orthogonal to said axial direction AA and to said radial direction RR.

[0055] According to an embodiment, the piston 10 has a ventilation chamber depth P1 and a thrust seat depth P2. The ventilation chamber depth P1 is defined by a first distance along the axial direction AA between a central portion of the first pad side surface 15 and an orthogonal projection of the first annular edge 12 in the axial direction AA. The thrust seat depth P2 is defined by a distance along the axial direction AA between a central portion of the second brake fluid side surface 16 and an orthogonal projection of the second annular edge 13 in the axial direction AA. The ventilation seat depth P1 is at least half of the thrust seat depth P2.

[0056] According to an embodiment, on the side of the second brake fluid side surface 16 , the spacer 14 delimits an undercut seat to accommodate an end portion of a thrust device. The undercut seat forms a narrowed portion of the thrust seat 18 .

[0057] According to an embodiment, said thrust seat 18 has a polygonal shape.

[0058] According to an embodiment, the piston 10 has a piston axis A parallel to the axial direction AA, about which the piston 10 extends symmetrically.

[0059] According to an embodiment, said side wall 11 comprises an outer side surface which delimits said piston 10 externally with respect to said vent chamber 17 and said thrust seat 18. According to an embodiment, said outer side surface is a substantially cylindrical surface.

[0060] According to an embodiment, the side wall 11 comprises a first inner side surface 30 and a second inner side surface 31 which delimit the piston 10 by facing internally the ventilation chamber 17 and the thrust seat 18 , respectively.

[0061] According to an embodiment, the first inner surface 30 has a first inner diameter Di1 , and the second inner surface 31 has a second inner diameter Di1 .

[0062] According to an embodiment, the first inner diameter Di1 is equal to at least one third greater than the second inner diameter Di1. According to an embodiment, the first inner diameter Di1 is at least twice as large as the second inner diameter Di1.

[0063] According to an embodiment, the first inner surface 30 is a substantially cylindrical surface.

[0064] According to an embodiment, the second inner side surface 31 is a polygonal surface, such as the side surface of a parallelepiped, for example with a square base and rounded corners.

[0065] The invention also relates to a brake caliper for a disc brake, which is denoted overall by the reference numeral 1 .

[0066] The brake caliper 1 comprises at least one piston 10 according to at least one of the above-described embodiments.

[0067] The brake caliper 1 comprises a caliper body 2 adapted to be arranged to straddle a brake disc 32. The brake disc 32 has a first braking surface 33 and an opposite second braking surface 34, the brake disc 3 being adapted to rotate about an axis of rotation XX defining a direction parallel to the axial direction AA.

[0068] The caliper body 2 comprises a first caliper body part 6, which is adapted to directly or indirectly face the first braking surface 33. The caliper body 2 comprises at least one connecting bridge 8, which is supported by the first caliper body part 6 and which protrudes to straddle the brake disc 32. The caliper body 2 comprises a second caliper body part 7, which is supported to be cantilevered relative to the at least one floating element bridge 12 and is adapted to directly or indirectly face the second braking surface 4.

[0069] Said first caliper body portion 6 delimits internally a piston or cylinder seat 9 which is suitable for accommodating at least one said piston 10 in a fluid-tight manner and in a sliding manner.

[0070] According to an embodiment, the first caliper body portion 6 comprises a cylindrical wall 35 and a bottom wall 36 defining the piston or cylinder seat 9. The bottom wall 36 is transverse to the cylindrical wall 35, extending parallel to the radial direction RR, and is made in one piece with the cylindrical wall 35.

[0071] According to an embodiment, said cylindrical wall 35 comprises a first cylindrical portion 37 and a second cylindrical portion 38 connected by a cylinder shoulder 39 extending mainly substantially parallel to said radial direction RR.

[0072] According to an embodiment, the first cylindrical portion 37 accommodates the first side wall portion 20 of the piston 10 in a sliding manner. The second cylindrical portion 38 accommodates the second cylindrical wall portion 21 of the piston 10 in a sliding manner.

[0073] According to an embodiment, the third annular edge 22 faces the cylinder shoulder 39, and the second annular edge 13 and the thrust seat 18 indirectly face the bottom wall 36, thereby defining a pressure chamber, and the brake fluid is injected into the pressure chamber through a duct 40 passing through the cylinder shoulder 39 to hydraulically bias the piston 10 at least during the application of the service brake.

[0074] According to an embodiment, said brake calliper 1 comprises thrust means 19 adapted to bias said piston 10 in a mechanical manner at least during application of the parking brake.

[0075] According to an embodiment, said thrust means 19 are partially housed in said thrust seat 18 and in said second cylindrical portion 38 between said bottom wall 36 and said second annular edge 22 of said piston 10 .

[0076] According to an embodiment, said thrust means 19 comprises at least one rotating member 41 coupled to a thrust member 42 , wherein a rotation of said rotating member 41 corresponds to a translation of said thrust member 42 integral with said piston 10 .

[0077] According to an embodiment, the rotating member 41 is rotatably accommodated in a rotating seat 43 in a sealed manner and passes through the bottom wall 36, so that the rotating member 41 can rotate around a rotation axis basically parallel to the axial direction AA when connected to an electric motor 44 that can be constrained to the caliper body 2. The rotating seat 43 is formed in the bottom wall 36 of the cylinder 9.

[0078] According to an embodiment, the thrust device 19 comprises a screw-nut screw assembly. According to an embodiment, the rotating member 41 is a screw and the thrust piece 42 is a nut accommodated in the thrust seat 18. According to an embodiment, the nut comprises a threaded hollow body having a generally cylindrical shape and the nut comprises a plurality of petals protruding radially outward from the hollow body to fit into the thrust seat 18, thereby allowing the piston 10 to slide forward relative to the plurality of petals when biased by the brake fluid and allowing the nut to travel in a manner integral with the piston when the thrust device 19 biases the piston 10.

[0079] According to an embodiment, the thrust device 19 comprises a ball-in-ramp device connecting the rotating member 41 to the thrust device 42. Such a ball-in-ramp device is known, for example, from document US20150323026A1.

[0080] According to an embodiment, the brake caliper 1 includes a motor unit connected to the caliper body 2 , wherein the motor unit includes an electric motor 44 and a reduction gear box 45 , wherein the reduction gear box 45 is connected to the rotating member 41 .

[0081] According to an embodiment, the brake caliper 1 is a floating caliper.

[0082] According to an embodiment, the brake caliper 1 comprises a bracket 3 adapted to be connected to a caliper bracket provided in a vehicle. According to an embodiment, the caliper body 2 is supported by said bracket 3 in a sliding manner to move relative to the bracket 3 in said axial direction AA.

[0083] According to an embodiment, the bracket 3 supports the first brake pad 4 and the second brake pad 5 in a sliding manner. According to an embodiment, the brake caliper 1 is a single-piston caliper.

[0084] According to an embodiment, said first caliper body part 6 has, according to an embodiment, outside the piston or cylinder seat 9 , a caliper body shoulder 46 which externally reduces the radial dimension of the caliper body between the first cylindrical part 37 and the second cylindrical part 38 .

[0085] According to an embodiment, said brake calliper 1 comprises at least one electromechanical parking brake (EPB).

[0086] It is obvious that a person skilled in the art will be able to change or modify the present invention without departing from the scope of the appended claims.

[0087] Reference numerals list

[0088] 1. Brake calipers

[0089] 2. Caliper body

[0090] 3. Bracket

[0091] 4. First brake pad

[0092] 5. Second brake pad

[0093] 6. First caliper body portion or first elongated portion

[0094] 7. Second elongated portion or second caliper body portion

[0095] 8. Bridge for connection

[0096] 9. Seating part for piston or cylinder

[0097] 10. Piston

[0098] 11. Sidewall

[0099] 12. First annular edge or thrust edge

[0100] 13. Second ring edge

[0101] 14. Spacers or transverse spacers

[0102] 15. First pad side surface

[0103] 16. Second brake fluid side surface

[0104] 17. Ventilation room

[0105] 18. Thrust seat

[0106] 19. Thrust device

[0107] 20. First side wall portion

[0108] 21. Second side wall portion

[0109] 22. Third ring edge

[0110] 23. Central part of the partition

[0111] 24. Partition peripheral part

[0112] 25. Contact teeth

[0113] 26. Concave

[0114] 27. First tubular portion

[0115] 28. Second tubular portion

[0116] 29. Third tubular portion

[0117] 30. First inner surface

[0118] 31. Second inner surface

[0119] 32. Brake disc

[0120] 33. First braking surface

[0121] 34. Second braking surface

[0122] 35. Cylindrical wall

[0123] 36. Bottom wall

[0124] 37. First cylindrical part

[0125] 38. Second cylindrical part

[0126] 39. Cylinder shoulder

[0127] 40. Pipeline

[0128] 41. Rotating components

[0129] 42. Thrust member

[0130] 43. Rotating seat

[0131] 44. Electric motor

[0132] 45. Reduction gear box

[0133] 46. ​​Caliper body shoulder

[0134] De1 First outer diameter

[0135] De2 Second outer diameter

[0136] Di1 First Internal Diameter

[0137] Di2 Second Internal Diameter

[0138] S1 First Thickness

[0139] S2 Second thickness

[0140] S3 Third Thickness

[0141] A1 First axial length

[0142] A2 Second axial length

[0143] A3 Third axial length

[0144] P1 Ventilation chamber depth

[0145] P2 Thrust seat depth

[0146] A Piston axis

[0147] XX disk axis

[0148] De1 first outer diameter.

Claims

1. A piston (10) for a brake caliper (1), the piston (10) comprising: a side wall (11) extending mainly in an axial direction (AA) between a first annular edge (12) and a second annular edge (13), the first annular edge (12) being configured to contact the first brake pad (4) and the second annular edge (13) being configured to receive thrust from a brake fluid, a spacer portion (14), the spacer portion (14) extending at least in a radial direction (RR), wherein the radial direction (RR) is transverse to the axial direction (AA), wherein the spacer portion (14) comprises a first pad side surface (15) and a second brake fluid side surface (16), the first pad side surface (15) being adapted to face the first brake pad (4), wherein the side wall (11) and the spacer (14) delimit a thrust seat (18) and a ventilation chamber (17), wherein the thrust seat (18) and the ventilation chamber (17) are fluidically separated by the spacer (14) along the axial direction (AA), wherein the thrust seat (18) is open at the second annular edge (13) and closed at the second brake fluid side surface (16), wherein the thrust seat (18) is adapted to receive a thrust device (19) to at least partially mechanically actuate the piston (10) to bias the first brake pad (4), wherein the ventilation chamber (17) is open at the first annular edge (12) and is closed at least by the first pad side surface (15), wherein the ventilation chamber (17) is suitable for receiving air to thermally insulate the partition (14), The side wall (11) comprises a first side wall portion (20) and a second side wall portion (21), the first side wall portion (20) has a first outer diameter (De1), the second side wall portion (21) has a second outer diameter (De2), the first outer diameter (De1) is greater than the second outer diameter (De2), wherein the first side wall portion (20) internally delimits at least the ventilation chamber (17), wherein the second side wall portion (21) at least partially delimits the thrust seat (18) internally, The piston (10) comprises a third annular edge (22), which mainly extends along the radial direction (RR), wherein the third annular edge (22) externally connects the first side wall portion (20) and the second side wall portion (21) in an undercut manner to receive the thrust from the brake fluid.

2. The piston (10) according to the preceding claim, wherein The spacer (14) includes a central portion (23) and a peripheral portion (24) on one side of the first pad side surface (15), wherein the central portion (23) is convex relative to the peripheral portion (24), and / or wherein the peripheral portion (24) is concave relative to the central portion (23).

3. Piston (10) according to the preceding claim, wherein The central portion (23) has a circular or bone-shaped shape, and wherein the peripheral portion (24) has an annular crown or crescent-shaped shape.

4. The piston (10) according to any one of the preceding claims, wherein The first annular edge (12) comprises at least one contact tooth (25) and at least one recess (26), wherein the at least one contact tooth (25) is raised relative to the at least one recess (26) along the axial direction (AA) or in a direction parallel to the axial direction (AA), so that when the at least one tooth (25) contacts the first brake pad (4), the recess (26) forms a radial window with the side wall (11), and the radial window is suitable for allowing air to enter and exit the ventilation chamber (17) and reducing the contact surface between the first annular edge (12) and the first brake pad (4).

5. Piston (10) according to the preceding claim, wherein The central portion (23) has a circular or bone-shaped shape, and wherein the peripheral portion (24) has an annular crown or crescent shape; And / or wherein the first annular edge (12) comprises a plurality of the at least one contact toothed portion (25) and a plurality of the at least one recessed portion (26) alternately arranged along the circumference of the first annular edge (12).

6. The piston (10) according to any one of the preceding claims, wherein The first side wall portion (20) comprises a first tubular portion (27), wherein the first tubular portion (27) has a first thickness (S1) and a first axial length (A1), wherein the second side wall portion (21) comprises a second tubular portion (28), wherein the second tubular portion (28) is connected to the first tubular portion (27), wherein the second tubular portion (28) has a second thickness (S2) and a second axial length (A2), wherein The first axial length (A1) is at least equal to the second axial length (A2), wherein the first thickness (S1) is at least equal to the second thickness (S2), The first tubular portion (27) delimits the ventilation chamber (17) internally, and the second tubular portion (28) at least partially delimits the thrust seat (18).

7. Piston (10) according to the preceding claim, in, The first side wall portion (20) comprises a third tubular portion (29) disposed between the first tubular portion (27) and the second tubular portion (29), wherein the third tubular portion (29) is connected to the second tubular portion (28) via the third annular edge (22), wherein the third tubular portion (29) has a third thickness (S3) and a third axial length (A3), wherein the third thickness (S3) is at least twice the first thickness (S1), wherein the third thickness (A3) is twice the first thickness (S1), wherein the first axial length (A1) is greater than the third axial length (A3), so that the third tubular portion (29) forms a radiator portion between a third annular edge (22) facing the brake fluid and the first tubular portion (27); And / or wherein the first tubular portion (27) and the spacer (14) form a cup-shaped portion.

8. Piston (10) according to the preceding claim, in, The first tubular portion (27) and the spacer (14) form a cup-shaped portion, And / or wherein the second tubular portion (28) and the third tubular portion (29) and the spacer (14) form a T-shaped portion, wherein the third tubular portion (29) forms a restricted handle of the T-shaped portion, and the third tubular portion (29) connected to the spacer (14) forms a head of the T-shaped portion.

9. The piston (10) according to any one of the preceding claims, in, The first pad side surface (15) and the second brake fluid side surface (16) are diametrically opposed along the axial direction (AA), wherein the first pad side surface (15) and the second brake fluid side surface (16) comprise respective central portions extending primarily in a direction parallel to the radial direction (RR), wherein the first annular edge (12) and the second annular edge (13) extend mainly in a direction parallel to the radial direction (RR) and form opposite axial ends of the piston (10), wherein the first annular edge (12) and the second annular edge (13) extend mainly along a circumferential direction (CC) exactly orthogonal to the axial direction (AA) and the radial direction (RR), respectively, The piston (10) has a ventilation chamber depth (P1) and a thrust seating depth (P2). wherein the thrust chamber depth (P1) is defined by a first distance along the axial direction (AA) between a central portion of the first pad side surface (15) and an orthogonal projection of the first annular edge (12) in the axial direction (AA), and wherein the thrust seating portion depth (P2) is defined by a distance along the axial direction (AA) between a central portion of the second brake fluid side surface (16) and an orthogonal projection of the second annular edge (13) in the axial direction (AA), wherein the ventilation seating portion depth (P1) is at least half of the thrust seating portion depth (P2).

10. The piston (10) according to any one of the preceding claims, wherein The side wall (11) includes an outer surface, which limits the piston (10) externally relative to the ventilation chamber (17) and the thrust seat (18), wherein the side wall (11) includes a first inner surface (30) and a second inner surface (31), and the first inner surface (30) and the second inner surface (31) limit the piston (10) by facing the ventilation chamber (17) and the thrust seat (18) internally, respectively, wherein the first inner surface (30) has a first inner diameter (Di1), and the second inner surface (31) has a second inner diameter (Di1), wherein the first inner diameter (Di1) is at least one third larger than the second inner diameter (Di1), and preferably, the first inner diameter (Di1) is at least twice the second inner diameter (Di1).

11. Piston (10) according to the preceding claim, in, The outer surface is a substantially cylindrical surface, and / or where The first inner surface (30) is a substantially cylindrical surface, And / or wherein the second inner surface (31) is a polygonal surface, and the second inner surface (31) is, for example, a side surface of a square-base parallelepiped.

12. A brake caliper (1) of the floating type for a brake disc caliper, the brake caliper (1) comprising: at least one piston (10) according to any one of the preceding claims, A caliper body (2) adapted to be mounted astride a brake disc (32), the brake disc (32) having a first braking surface (33) and an opposite second braking surface (34), the brake disc (3) being adapted to rotate about a rotation axis (XX), the rotation axis (XX) defining a direction parallel to the axial direction (AA), Wherein, the caliper body (2) comprises a first caliper body part (6), and the first caliper body part (6) is suitable for directly or indirectly facing the first braking surface (33); wherein the caliper body element (2) comprises at least one connecting bridge (8), the connecting bridge (8) being supported by the first floating element portion (6), and the connecting bridge (8) protruding to straddle the brake disc (32); wherein the caliper body (2) comprises a second caliper body part (7), the second caliper body part (7) being supported in a cantilevered manner to the at least one floating element bridge (12), and the second caliper body part (7) being adapted to directly or indirectly face the second braking surface (4), wherein the first caliper body portion (6) internally delimits a piston or cylinder seat (9), the piston or cylinder seat (9) being adapted to accommodate at least one of the pistons (10) in a fluid-tight manner, wherein the first caliper body portion (6) comprises a cylindrical wall (35) and a rear wall (36), the cylindrical wall (35) and the rear wall (36) defining the piston or cylinder seat (9), wherein the rear wall (36) is transverse to the cylindrical wall (35) and extends parallel to the radial direction (RR), and the rear wall (36) is made in one piece with the cylindrical wall (35); wherein the cylindrical wall (35) comprises a first cylindrical portion (37) and a second cylindrical portion (38) connected by a cylinder shoulder (39), wherein the cylinder shoulder (39) extends mainly parallel to the radial direction (RR), wherein the first cylindrical portion (37) accommodates the first side wall portion (20) of the piston (10) in a sliding manner, and wherein the second cylindrical portion (38) accommodates the second cylindrical wall portion (21) of the piston (10) in a sliding manner, wherein the third annular edge (22) faces the cylinder shoulder (39), and wherein the second annular edge (13) and the thrust seat (18) indirectly face the rear wall (36), thereby defining a pressure chamber into which brake fluid is injected through a duct (40) passing through the cylinder shoulder (39), thereby hydraulically pressurizing the piston (10) at least during service braking, The brake caliper (1) comprises a thrust device (19) adapted to mechanically pressurize the piston (10) at least during parking braking. wherein the thrust device (19) is partially housed in the thrust seat (18) and in the second cylindrical portion (38) between the bottom wall (36) and the second annular edge (22) of the piston (10), wherein the thrust device (19) comprises at least one rotating member (41) coupled to a thrust member (42); The rotating member (41) is rotatably accommodated in a rotating seat (43) formed in the bottom wall (36) of the cylinder (9) in a sealed manner and passes through the bottom wall (36), so that the rotating member (41) can rotate around a rotation axis substantially parallel to the axial direction (AA) when connected to an electric motor (44) capable of being constrained to the caliper body (2), The rotation of the rotating member (41) corresponds to the translation of the thrust member (42) which is integral with the piston (10).

13. Brake caliper (1) according to the preceding claim, wherein: The first caliper body part (6) comprises a cylindrical wall (35) and a rear wall (36), the cylindrical wall (35) and the rear wall (36) defining the piston or cylinder seat (9), wherein the rear wall (36) is transverse to the cylindrical wall (35) and extends parallel to the radial direction (RR), and the rear wall (36) is made in one piece with the cylindrical wall (35); wherein the cylindrical wall (35) comprises a first cylindrical portion (37) and a second cylindrical portion (38) connected by a cylinder shoulder (39), wherein the cylinder shoulder (39) extends mainly parallel to the radial direction (RR), wherein the first cylindrical portion (37) accommodates the first side wall portion (20) of the piston (10) in a sliding manner, and wherein the second cylindrical portion (38) accommodates the second cylindrical wall portion (21) of the piston (10) in a sliding manner, wherein the third annular edge (22) faces the cylinder shoulder (39), and wherein the second annular edge (13) and the thrust seat (18) indirectly face the rear wall (36), thereby defining a pressure chamber into which brake fluid is injected through a duct (40) passing through the cylinder shoulder (39), thereby hydraulically pressurizing the piston (10) at least during service braking, The brake caliper (1) comprises a thrust device (19) adapted to mechanically pressurize the piston (10) at least during parking braking, wherein the thrust device (19) is partially housed in the thrust seat (18) and in the second cylindrical portion (38) between the bottom wall (36) and the second annular edge (22) of the piston (10), wherein the thrust device (19) comprises at least one rotating member (41) coupled to a thrust member (42); The rotating member (41) is rotatably accommodated in a rotating seat (43) formed in the bottom wall (36) of the cylinder (9) in a sealed manner and passes through the bottom wall (36), so that the rotating member (41) can rotate around a rotation axis substantially parallel to the axial direction (AA) when connected to an electric motor (44) capable of being constrained to the caliper body (2), The rotation of the rotating member (41) corresponds to the translation of the thrust member (42) which is integral with the piston (10).

14. Brake caliper (1) according to the preceding claim, wherein: The thrust device (19) comprises a screw-nut assembly, wherein the rotating member (41) is a screw, and the thrust device (42) is a nut accommodated in the thrust seat (18). or wherein the thrust device (19) comprises a ball ramp device, wherein the ball ramp device connects the rotating member (41) to the thrust device (42), and / or wherein the brake caliper (1) comprises a motor unit, the motor unit being connected to the caliper body (2), wherein the motor unit comprises an electric motor (44) and a reduction gearbox (45), wherein the reduction gearbox (45) is connected to the rotating member (41), And / or wherein the brake caliper (1) is a floating type caliper, the brake caliper (1) comprises a bracket (3), the bracket (3) is suitable for connecting to a caliper bracket provided in a vehicle; wherein the bracket (3) supports the first brake pad (4) and the second brake pad (5) in a sliding manner, The caliper body (2) is supported by the bracket (3) in a sliding manner so as to move relative to the bracket (3) along the axial direction (AA). And / or wherein the brake caliper (1) is a single-piston caliper.

15. The brake caliper (1) according to any one of claims 12 to 14, wherein: The first caliper body portion (6) has a caliper body shoulder (46) located outside the piston or cylinder seat (9), and the caliper body shoulder (46) externally reduces the radial dimension of the caliper body between the first cylindrical portion (37) and the second cylindrical portion (38).

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