Thrust actuator, braking device

Abstract

The subject matter of the present invention is a thrust actuator (1) for a braking device (100), for example a brake caliper, wherein the thrust actuator (1) comprises a piston (3), wherein the piston (3) comprises a thrust head (4), wherein the thrust head (4) is configured to transfer directly or indirectly the thrust force to the lever head (6), wherein the piston (3) has a piston axis (X), a transformation assembly (21), wherein the transformation assembly (21) comprises a rotating member (22) and a thrust member (23), wherein the thrust member (23) is mechanically coupled to the piston (3), wherein the rotating member (22) is mechanically coupled to the thrust member (23) so as to transform a rotation of the rotating member (22) into a linear translation of the thrust member (23) which enables a reversible linear displacement along the thrust direction (X-X) of the piston (3), wherein the rotating member (22) is configured to receive a torque from an electric motor (20), either directly or indirectly via a transmission (24), wherein the thrust direction (X-X) of the piston (3) is parallel to an axial direction (A-A) and perpendicular to both the radial direction (R-R) and the tangential direction (T-T), an actuator body (18) configured to accommodate and support the transformation assembly (21) and the piston (3), wherein the actuator body (18) delimits a housing opening (12), and comprises at least one housing side wall (13) and at least one housing shoulder (11), wherein the at least one housing side wall (13) extends at least from the at least one housing shoulder (11) to the housing opening (12), delimiting a housing (19) configured to house the transformation assembly (21) and the piston (3), wherein the piston (3) is housed in the housing (19) translationally movable along the thrust direction (X-X) between a rest position (A0) and a thrust position (A1), reversibly projecting the thrust head (4) from the housing opening (12) under actuation of the electric motor (20), a detection sensor (9), wherein the detection sensor (9) is connected to the actuator body (18) and is arranged axially downstream of the transformation assembly (21) on the side opposite the housing opening (12) so as to detect, either directly or indirectly, a reaction force opposite to the thrust force (FA) discharged from the piston (3) to the transformation assembly (21), a bushing (17), wherein the bushing (17) is constrained to the actuator body (18) at the housing opening (12), wherein the bushing (17) is coupled to the piston (3) by constraining the thrust head (4) to translate in a direction parallel to the piston axis (X) and preventing the piston (3) from oscillating about directions incident or perpendicular to the piston axis (X), wherein the bushing (17) is configured to support the piston (3) in translation by discharging onto the bushing (17) any radial component of the thrust force with respect to the thrust direction (X-X) and preventing misalignment of the piston (3) inside the housing (19).

Description

Thrust actuator, braking deviceDESCRIPTION

[0001] . Field of the invention

[0002] . The subject matter of the present invention is a thrust actuator and a braking device, for example a brake caliper, preferably for braking systems for heavy-duty vehicles (heavy duty or heavy vehicles, for example trucks or lorries, road trains, articulated lorries). The thrust actuator is preferably an electromechanical thrust actuator for a braking device, preferably a purely translational electromechanical thrust actuator.

[0003] . Prior art

[0004] . Braking systems provide at least one thrust device configured to actuate an advancement of at least one brake pad of a disc brake or a shoe of a drum brake towards a braking surface, in order to brake a vehicle.

[0005] . In braking systems for heavy vehicles, in order to actuate the thrust device, a mechanism is provided comprising a thrust piston actuatable while advancing along a linear direction and a rotatable lever configured to actuate, with mechanical advantage, an advancement of the thrust piston, for example by means of a gear system.

[0006] . The thrust piston is configured to interact with a thrust seat formed at one end of the lever to command a rotation of the lever, and consequently actuate the thrust device.

[0007] . The thrust seat of the lever is usually formed as a spherical recess, suitable for receiving a spherical tip arranged at the end of the thrust piston.

[0008] . The thrust piston is configured to transmit the force along a linear direction, whereas the spherical recess rotates along a circumferential direction about the fulcrum of the lever, and consequently force components are generated between the thrust piston and the lever along directions radial with respect to the linear direction, which reduce the efficiency of motion transmission from the piston to the lever.

[0009] . In the case of pneumatic actuation of the thrust piston, as known for example from document EP1650464, the thrust piston is connected to a pneumatic device by means of an elastically deformable membrane which allows the thrust piston to translate linearly, also along directions inclined with respect to the linear direction of maximum efficiency under the action of force components along the radial directions, preventing the force components along the radial directions from inducing stress conditions that could compromise the translation and operation of the thrust piston.

[0010] . In the case of electromechanical actuation of the thrust piston, the thrust piston translates mechanically along the thrust direction under the action, for example, of a screw-nutassembly, and it has been found that the force components along the radial directions induce, at the interface between piston and lever, stress conditions which, in addition to reducing the efficiency of motion transmission, cause possible malfunctions in the screw-nut assembly and, in extreme cases, failures in the system.

[0011] . Document EP4386233 discloses an electromechanical thrust actuator in which the thrust piston is connected to the translational thrust mechanism, such as a screw-nut assembly, by means of a pivot joint so as to incline the thrust piston in contact with the lever as it rotates.

[0012] . This solution, although satisfactory in some respects, introduces mechanical complexity in the electromechanical thrust actuator, as well as reducing the efficiency of motion transmission, and furthermore makes it difficult to reliably and safely control and predict over time the forces actually transmitted by the electromechanical thrust actuator to the braking element that brakes the vehicle. In particular, with this solution, since the thrust piston is oscillatable, the position of the head of the thrust piston acts on the lever by changing position for each angle of rotation of the lever, introducing high complexity in controlling the actuation of the braking device, with a high variability between the thrust force transmitted to the lever and the output force transmitted by the lever to the thrust device to brake a rotating braking surface, for example a brake disc.

[0013] . There is therefore a strongly felt need in the field to implement thrust actuators for actuating a braking lever of a braking device, which allow increasing the efficiency of transmission of the thrust from the thrust actuator to the rotatable lever, as well as enabling control of each angle of rotation of the rotatable lever through the translation of the piston of the thrust actuator.

[0014] . Solution

[0015] . The present invention aims to provide a thrust actuator, as well as a braking device comprising the thrust actuator.

[0016] . These and other aims are achieved by means of a thrust actuator and a braking device according to the independent claims.

[0017] . Some advantageous embodiments are the subject matter of the dependent claims.

[0018] . This solution makes it possible to achieve a purely translational actuation of the thrust piston, preventing force components along directions incident or radial to the thrust direction from being transmitted to the transformation mechanism, for example a screw-nut mechanism, thereby increasing the efficiency of thrust transmission from the translating piston to the rotating lever, as well as the reliability and durability of the thrust actuator.

[0019] . Thanks to the proposed solutions, it is possible to constrain the translation of the thrust piston that actuates the rotating lever by detecting the axial force transmitted by the thrust piston and, knowing the coefficient of friction between the thrust piston and the rotating lever, it is possible to control the friction forces between the thrust piston and the rotating lever, and consequently, knowingthe lever ratio provided by the lever multiplying mechanism and the input force of the braking device given by the thrust actuator and the friction forces, it is possible to control the output force, given by the pressing force on the rotating braking surface, for example the brake disc. In this way, it is possible to achieve a precise and constant control between the thrust force of the thrust actuator and the braking force on the brake disc or on the rotating braking surface.

[0020] . Thanks to the proposed solutions, it is also possible to increase the efficiency of transmission of the thrust action from a thrust actuator to a rotating lever, as well as to avoid implementing solutions that allow a deviation of the translation of the thrust piston from the rectilinear thrust direction.

[0021] . Thanks to the proposed solutions, it is possible to actuate service brakes and parking brakes for heavy vehicles electromechanically in a highly efficient manner.

[0022] . Figures

[0023] . Further features and advantages of the invention will appear from the following description of its preferred embodiments, given by way of non-limiting example, with reference to the accompanying figures in which:

[0024] . - Figure 1 schematically shows a braking device, in particular a brake caliper, comprising a thrust device configured to actuate a brake pad, wherein the thrust device is actuatable by a lever mechanism, wherein the lever of the lever mechanism is actuated in rotation by a thrust actuator according to the present invention comprising a thrust piston which is electrically actuated by an electric motor, wherein the thrust piston is constrained to translate along the rectilinear thrust direction avoiding oscillations of the piston supported by a bushing forming a translational sleeve constraint;

[0025] . - Figure 2 illustrates a side view in section along a thrust axis of the thrust member, a thrust actuator according to the present invention connected to a braking device, for example as the brake caliper of figure 1, wherein an interface ball is visible interposed between a partially spherical recess of a lever head placed at the end of the lever opposite the rotation fulcrum, and a thrust head having a sliding recess or concave sliding track arranged at the end of a piston translatable along the thrust direction by action of an electric motor, wherein the bushing supporting the translation of the thrust piston by discharging each non-purely translational component generated by the interaction of the thrust piston with the lever, forms a fluid-tight connection with the braking device, as well as a sealing connection with the thrust piston preventing dust or dirt from entering the body of the thrust actuator;

[0026] . - Figure 3 shows a thrust actuator according to the present invention sectioned along a plane passing through the axis of the thrust piston, rectilinear and parallel to the thrust direction, wherein the thrust piston is a stepped piston comprising a proximal piston portion and a distal pistonportion, wherein the proximal piston portion has a greater diameter than the distal piston portion, wherein the distal piston portion is supported in translation by the bushing, and wherein the proximal piston portion is slidable in contact with a housing side wall of the actuator body, in such a way that the piston is slidable and supported in two axially spaced zones with different diameters, avoiding misalignment of the thrust piston.

[0027] . - Figure 4 shows an exploded axonometric view of the thrust actuator of figure 3;

[0028] . - Figure 5 shows a schematic view of a thrust actuator according to the present invention, wherein the transformation mechanism of the rotational motion of the electric motor into translational motion of the thrust piston is a screw-nut assembly, wherein the screw rotates and is directly or indirectly connected to a shaft of the motor, and the nut translates by directly or indirectly pushing the thrust piston, wherein the thrust piston is in a rest position;

[0029] . - Figure 6 schematically shows the thrust actuator of figure 5, wherein the thrust piston is in an advanced thrust position;

[0030] . - Figure 7 shows a schematic view of a thrust actuator according to the present invention, wherein the transformation mechanism of the rotational motion of the electric motor into translational motion of the thrust piston is a screw-nut assembly, wherein the nut rotates and is directly or indirectly connected to a shaft of the motor, and the screw translates by directly or indirectly pushing the thrust piston, wherein the thrust piston is in a rest position;

[0031] . - Figure 8 schematically shows the thrust actuator of figure 7, wherein the thrust piston is in an advanced thrust position.

[0032] . Description of some preferred embodiments

[0033] . According to a general embodiment, a thrust actuator for a braking device 100, for example a brake caliper, is denoted by reference number 1.

[0034] . The braking device 100 comprises a thrust device 101, for example a brake caliper piston or a drum brake piston, configured to translationally actuate a friction element 102 against a braking surface 103 for braking a vehicle.

[0035] . The braking device 100 comprises a lever 5, wherein the lever 5 is rotationally movable about a rotation axis R parallel to a tangential direction T-T. The lever 5 comprises a lever head 6 integrally rotationally movable at one end of the lever 5. The lever head 6 is configured to receive a thrust force. The lever 5 is mechanically connected to the thrust device 101 so that by rotating it actuates in translation the thrust device 101 to translationally actuate the friction element 102 for braking the vehicle.

[0036] . The thrust actuator 1 comprises a piston 3. The piston 3 comprises a thrust head 4. The thrust head 4 is configured to transfer directly or indirectly the thrust force to the lever head 6. The piston 3 has a piston axis X, for example around and along which it extends.

[0037] . The thrust actuator 1 comprises a transformation assembly 21. The transformation assembly 21 comprises a rotating member 22 and a thrust member 23. The thrust member 23 is mechanically coupled to the piston 3. The rotating member 22 is mechanically coupled to the thrust member 23 so as to transform a rotation of the rotating member 22 into a linear translation of the thrust member 23 which enables a reversible linear displacement along the thrust direction X-X of the piston 3. The rotating member 22 is configured to receive a torque from an electric motor 20, either directly or indirectly through a transmission 24. The thrust direction X-X of the piston 3 is parallel to an axial direction A-A and perpendicular to both the radial direction R-R and the tangential direction T-T. In one embodiment, the piston axis X is parallel to the thrust direction X-X.

[0038] . The thrust actuator 1 comprises an actuator body 18 configured to accommodate and support the transformation assembly 21 and the piston 3. The actuator body 18 defines a housing opening 12, and the actuator body 18 comprises at least one housing side wall 13 and at least one housing shoulder 11. The at least one housing side wall 13 extends at least from the at least one housing shoulder 11 to the housing opening 12, defining a housing 19 configured to house the transformation assembly 21 and the piston 3.

[0039] . The piston 3 is housed in the housing 19 translationally movable along the thrust direction X-X between a rest position A0 and a thrust position A1, projecting the thrust head 4 from the housing opening 12 in a reversible manner under actuation of the electric motor 20.

[0040] . The thrust actuator 1 comprises a detection sensor 9. The detection sensor 9 is connected to the actuator body 18 and is arranged axially downstream of the transformation assembly 21 on the side opposite the housing opening 12 so as to detect, either directly or indirectly, a reaction force opposite to the thrust force FA discharged from the piston 3 to the transformation assembly 21.

[0041] . Advantageously, the thrust actuator 1 comprises a bushing 17.

[0042] . The bushing 17 is constrained to the actuator body 18 at the housing opening 12.

[0043] . The bushing 17 is coupled to the piston 3 by constraining the thrust head 4 and / or the piston 3 to translate in a direction parallel to the piston axis X and preventing the piston 3 from oscillating about directions incident or perpendicular to the piston axis X.

[0044] . In one embodiment, the bushing 17 is configured to support and / or supports the piston 3 in translation by discharging onto the bushing 17 any radial component of the thrust force with respect to the thrust direction X-X and preventing misalignment of the piston 3 inside the housing 19.

[0045] . In one embodiment, the bushing 17 comprises at least one bushing guide surface 35. In one embodiment, the bushing guide surface 35 defines a bushing diameter perpendicular to the piston axis X.

[0046] . In one embodiment, the piston 3 comprises a proximal piston portion 14 and a distal piston portion 15.

[0047] . In one embodiment, the proximal piston portion 14 is connected to the transformation assembly 21 and defines a piston cavity 16 to at least partially accommodate the transformation assembly 21.

[0048] . In one embodiment, the distal piston portion 15 is connected to the thrust head 4 or comprises the thrust head 4.

[0049] . In one embodiment, the distal piston portion 15 comprises at least one distal sliding surface 39. In one embodiment, the distal sliding surface 39 defines a distal portion diameter perpendicular to the piston axis X.

[0050] . In one embodiment, each distal sliding surface 39 translationally slides in contact with a respective one of the at least one bushing guide surface 35 so as to support the piston 3 in translation by discharging onto the bushing 17 radial components of the thrust force with respect to the thrust direction X-X and preventing misalignment of the piston 3 inside the housing 19. In one embodiment, the bushing diameter and the distal portion diameter are substantially equal to the bushing diameter, allowing low-friction sliding between the piston and the bushing.

[0051] . In one embodiment, the at least one housing side wall 13 comprises at least one side wall guide surface 34. In one embodiment, the side wall guide surface 34 defines a side wall diameter perpendicular to the piston axis X. In one embodiment, the side wall diameter is greater than the bushing diameter.

[0052] . In one embodiment, the piston 3 is a stepped piston.

[0053] . In one embodiment, the proximal piston portion 14 is connected to the distal piston portion 15 by reducing the diameter of the piston 3, forming the stepped piston.

[0054] . In one embodiment, the proximal piston portion 14 comprises at least one proximal sliding surface 38. In one embodiment, the at least one proximal sliding surface 38 defines a proximal portion diameter perpendicular to the piston axis X. In one embodiment, the proximal portion diameter is greater than the distal portion diameter.

[0055] . In one embodiment, each proximal sliding surface 38 translationally slides in contact with a respective one of the at least one side wall guide surface 34, for example avoiding a rotation of the piston 3 about the thrust direction X-X. In one embodiment, the side wall diameter is substantially equal to the proximal portion diameter so as to allow sliding between the piston and the side wall guide surface 34.

[0056] . In one embodiment, the piston 3 is slidingly guided and supported by at least two zones having different diameters, for example by the bushing 17 and the at least one housing side wall 13.

[0057] . In one embodiment, the piston 3 is guided, for example, by the bushing guide surfacebushing guide surface 35 extends at least partially within the housing 19 on the side axially opposite to the housing opening 12. In one embodiment, the bushing guide surface 35 is radially interposed between the distal piston portion 15 and the at least one side wall guide surface 34 along which the proximal piston portion 14 is slidable.

[0058] . Thanks to the provision of the bushing 17 and the stepped piston 3, it is possible to guide the piston in two guide portions having different diameters, constraining the translation of the piston 3 and supporting the piston in two different zones, thereby preventing misalignment of the piston within the housing and avoiding the transmission of radial forces to the transformation assembly 21.

[0059] . In one embodiment, the bushing 17 is coupled to the distal piston portion 15 in a sliding sealing manner, preventing the ingress of dust or moisture into the housing 19 from the outside.

[0060] . In one embodiment, the bushing 17 comprises a bushing hole 41 , wherein the bushing hole 41 is coaxial to the thrust direction X-X, and / or to the piston axis X. In one embodiment, the at least one bushing guide surface 35 defines the bushing hole 41. In one embodiment, the at least one distal sliding surface 39 defines the distal piston portion 15 radially with respect to the thrust direction X-X, and / or with respect to the piston axis X.

[0061] . In one embodiment, the at least one bushing guide surface 35 and the at least one distal sliding surface 39 are counter-shaped with respect to each other so as to slide over one another in a sealed manner, preferably with low friction.

[0062] . In one embodiment, the at least one bushing guide surface 35 is an annular surface, for example cylindrical, or lobed, forming an anti-rotational constraint. In one embodiment, the at least one bushing guide surface 35 is shaped defining a figure with at least one lobe, preferably a trilobed figure. In one embodiment, the at least one bushing guide surface 35 is an annular surface, for example cylindrical or lobed, forming an anti-rotational constraint. In one embodiment, the at least one bushing guide surface 35 is shaped defining a figure with at least one lobe, preferably a trilobed figure.

[0063] . In one embodiment, the at least one bushing guide surface 35 is a cylindrical surface, wherein the at least one distal sliding surface 39 is a cylindrical surface.

[0064] . In one embodiment, the proximal piston portion 14 is mechanically coupled to the at least one housing side wall 13 forming an anti-rotational constraint which prevents the piston 3 from rotating about the thrust direction X-X. In one embodiment, the proximal piston portion 14 and the at least one housing side wall 13 are counter-shaped so as to geometrically prevent the piston 3 from rotating within the housing 19 and / or wherein the proximal piston portion 14 has a piston groove 42 parallel to the axial direction A-A and the thrust actuator 1 comprises an anti-rotation pin 25 connected to the actuator body 18 projecting from the at least one housing side wall 13 so as to mechanically couple to the piston groove 42 preventing the piston 3 from rotating about the thrust direction X-X.

[0065] . In one embodiment, the thrust actuator 1 comprises a thrust bearing 10.

[0066] . In one embodiment, the thrust bearing 10 rotationally supports the rotating member 22.In one embodiment, the detection sensor 9 is arranged between the thrust bearing 10 and the housing shoulder 11 , to detect the reaction force, opposite to the thrust force, discharged from the piston 3 to the transformation assembly 21. In one embodiment, the detection sensor 9 is a force sensor. In one embodiment, the detection sensor 9 is a force sensor configured to elastically deform, generating a signal which is transmitted to a control unit via a sensor interconnector 30. In one embodiment, the sensor interconnector 30 is connected to the actuator body 18.

[0067] . In one embodiment, the transformation assembly 21 is a screw-nut assembly. In one embodiment, the screw-nut assembly is of the recirculating ball type. In one embodiment, the thrust member 23 comprises a nut, and the rotating member 22 comprises a worm screw, or vice versa.

[0068] . In one embodiment, the piston cavity 16 is a stepped cavity and comprises a proximal cavity portion 31 made in the proximal piston portion 14 and a distal cavity portion 32 made partially in the distal piston portion 15. In one embodiment, the piston 3 comprises an inner piston shoulder 36 axially between the proximal cavity portion 31 and the distal cavity portion 32. In one embodiment, the piston cavity 16 is closed on the side of the thrust head 4 and is open on the axially opposite side.

[0069] . In one embodiment, the thrust member 23 is housed in the proximal cavity portion 31 and is constrained to the proximal piston portion 14. In one embodiment, the actuator 1 comprises a thrust ring 26, for example configured to transfer the thrust force from the thrust member to the piston or vice versa. In one embodiment, the thrust ring 26 is axially arranged between the thrust member 23 and the inner piston shoulder 36. In one embodiment, the rotating member 22 is constrained to the thrust bearing 10.

[0070] . In one embodiment, the bushing 17 is a sliding bushing, wherein each bushing guide surface 35 is self-lubricating.

[0071] . In one embodiment, the bushing 17 comprises a matrix made of sintered material and lubricant particles trapped in the matrix made of sintered material, so that each bushing guide surface 35 is constantly lubricated, reducing friction during the sliding of the piston 3 through the bushing 17.

[0072] . In one embodiment, the bushing 17 comprises an axial sealing interface 43 configured to axially abut against a braking device body 104 of the braking device 100 so as to connect the thrust actuator 1 to the fluid-tight braking device 100.

[0073] . In one embodiment, the bushing 17 comprises an annular bushing body delimiting a bushing hole 41 and an annular bushing shoulder 37 radially projecting from the annular bushing body on the side opposite to the bushing hole 41. In one embodiment, the annular bushing shoulder 37 comprises a first bushing abutment surface 44 configured to abut against the actuator body 18. In one embodiment, the annular bushing body comprises a cantilevered portion projecting from the annularbushing shoulder 37 axially on the side opposite to the housing opening 12, inserting into the housing 19 in contact with the at least one housing side wall (13) and / or with the at least one side wall guide surface 34.

[0074] . In one embodiment, the annular bushing shoulder 37 comprises a second bushing abutment surface 45 on the axially opposite side to the first bushing abutment surface 44. In one embodiment, the second bushing abutment surface 45 defines an annular bushing groove 46. In one embodiment, the bushing 17 and / or the actuator 1 comprises an annular bushing gasket 47, for example an O-ring, wherein the annular bushing gasket 47 is housed in the annular bushing groove 46.

[0075] . In one embodiment, the axial sealing interface 43 comprises the second bushing abutment surface 45 and the annular bushing gasket 47.

[0076] . In one embodiment, the actuator body 18 comprises an annular bushing seat 50 configured to house the annular bushing shoulder 37 axially abutting against the second bushing abutment surface 45.

[0077] . In one embodiment, the actuator body 18 comprises an annular abutment edge 51 , arranged radially outside the annular bushing seat 50, wherein the annular abutment edge 51 is configured to axially abut against the braking device body 104 of the braking device 100 so as to connect the thrust actuator 1 to the fluid-tight braking device 100, in two distinct zones by means of both the bushing and the actuator body.

[0078] . In one embodiment, the annular abutment edge 51 comprises an actuator body groove 52, wherein the actuator 1 comprises an annular actuator gasket 53, for example an O-ring, wherein the annular actuator gasket 53 is housed in the actuator body groove 52.

[0079] . In one embodiment, the thrust actuator 1 comprises an electric motor 20. In one embodiment, the thrust actuator 1 comprises a transmission 24. In one embodiment, each electric motor 20 comprises a respective motor shaft 55. In one embodiment, each motor shaft 54 is connected to the transmission 24. In one embodiment, the transmission 24 is connected to the rotating member 22 so as to transfer the reduced rotation of the at least one motor shaft 55 from the transmission 24 to the rotating member 22. In one embodiment, the electric motor 20 is constrained to the actuator body 18. In one embodiment, the actuator body 18 defines a second housing configured to house the transmission 24.

[0080] . In one embodiment, the transmission 24 is a double-stage planetary transmission.

[0081] . In one embodiment, the transmission 24 comprises a first planetary gear stage 56.

[0082] . In one embodiment, the first planetary gear stage 56 comprises a first stage ring gear57, a first stage sun gear 60 connected to the motor shaft 55, three first stage planet gears 58, and a first stage planet carrier 59.

[0083] . In one embodiment, the first stage planet gears 58 are supported in rotation by the first stage planet carrier 59 through respective first stage pins 61, wherein the first stage planet gears 58 are configured to rotate inside the first stage ring gear 57 driven by the first stage sun gear 60.

[0084] . In one embodiment, the first stage planet carrier 59 comprises a sun-planetary interface 63 to interface with a second planetary gear stage 62 and / or with the rotating member of the transformation assembly 21.

[0085] . In one embodiment, the transmission 24 comprises a second planetary gear stage 62.

[0086] . In one embodiment, the second planetary gear stage 62 comprises a second stage sun gear 64, three second stage planet gears 65, a second stage ring gear 66, and a second stage planet carrier 67, wherein the second stage planet gears 66 are supported by the second stage planet carrier 67 through respective second stage pins 68, wherein the second stage sun gear 64 is rotationally constrained to the second stage planet carrier 67 through a rotation pin 69, wherein the second stage planet carrier 67 is rotationally supported by a transmission bearing 70.

[0087] . In one embodiment, the sun-planet interface 63 is constrained to the second stage sun gear 64 so as to transfer the rotation of the first planetary gear stage 56 to the second stage planet gears 65 rotating inside the second stage ring gear 66 together with the second stage planet carrier 67.

[0088] . In one embodiment, the second stage planet carrier 67 comprises a planet-rotating member interface 80 configured to connect the second planetary gear stage 62 to the rotating member 22.

[0089] . In one embodiment, the thrust actuator 1 is an electromechanical actuator.

[0090] . In one embodiment, the thrust actuator 1 is an electromechanical actuator avoiding hydraulic or pneumatic connections to actuate the piston 3.

[0091] . The present invention also concerns a braking device 100. In one embodiment, the braking device is a brake caliper.

[0092] . The braking device 100 comprises a braking device body 101 , for example a caliper body. The braking device body 104 defines a thrust housing 105 between an inlet opening 106 and an outlet opening 107.

[0093] . The braking device 100 comprises a lever 5, wherein the lever 5 is connected to the braking device body 101 and is housed in the thrust housing 105, wherein the lever 5 is rotationally movable about a rotation axis R parallel to or coincident with a tangential direction T-T, wherein the tangential direction T-T is perpendicular to a direction parallel to a thrust direction A-A, wherein the lever 5 comprises a lever head 6 integrally rotationally movable at one end of the lever 5.

[0094] . The braking device 100 comprises a thrust device 101, for example a brake caliper piston, wherein the thrust device 101 is housed in the thrust housing 105, wherein the thrust device101 is configured to translationally actuate a friction element 102 against a braking surface 103 to brake a vehicle, protruding from the outlet opening 107.

[0095] . The braking device 100 comprises a thrust actuator 1 according to any one of the embodiments previously described, wherein the actuator body 18 is connected to and supported by the braking device body 104, wherein the housing opening 12 faces the inlet opening 106 so that the thrust head 4 is translationally movable into the thrust housing 105.

[0096] . The thrust head 4 is configured to abut, either directly or indirectly, with the lever head 6 so as to transform the translation of the piston 3 into the rotation of the lever 5, wherein the lever 5 is mechanically connected to the thrust device 101 so that, by rotating, it translationally actuates the thrust device 101 to translationally actuate the friction element 102 to brake the vehicle.

[0097] . In one embodiment, the braking device 100 is an electromechanically actuated brake caliper.

[0098] . In one embodiment, the braking device 100 comprises an interface ball 7, wherein the interface ball 7 is interposed in abutment contact between the lever head 6 and the pusher head 4.

[0099] . In one embodiment, the lever head 4 defines a recess 8 configured to rotatably house the interface ball 7, and the thrust head 4 defines a concave sliding track 9 configured to house the interface ball 7 in translation and rotation, or vice versa, such that the interface ball 7 slides on the concave sliding track 9 rotating in the recess 8 as the piston 3 translates and the lever 5 rotates.

[0100] . In one embodiment, the braking device 100 is for heavy vehicles, and preferably is an electromechanically actuated brake caliper for heavy vehicles. In one embodiment, the braking device 100 is an electromechanically actuated brake caliper, wherein the thrust actuator 1 comprises an electric motor 20 so as to actuate the thrust device 101 via the lever 5 to actuate the brake caliper electromechanically. In one embodiment, the braking device 100 is a brake caliper for heavy vehicles, for example one among trucks or lorries, road trains, articulated lorries.

[0101] . Thanks to the proposed solutions, it is possible to implement a thrust actuator that allows improving the control and efficiency of thrust transfer from the translation of the thrust piston to the rotation of the lever that actuates the thrust device of the braking device, for example the brake caliper.

[0102] . Thanks to the proposed solutions, it is possible to implement a thrust actuator that allows translation without inclinations of the thrust piston in order to control and efficiently transfer the thrust action to the rotatable lever which in turn actuates the thrust device of the braking device, for example the brake caliper.LIST OF REFERENCES thrust actuator piston thrust head lever lever head interface ball recess detection sensor thrust bearing housing shoulder housing opening housing side wall proximal piston portion distal piston portion piston cavity bushing actuator body housing electric motor rotation-to-translation transformation assembly or screw-nut assembly rotating member thrust member transmission anti-rotation pin thrust ring fastening ring anti-rotation groove retaining ring sensor interconnector proximal cavity portion distal cavity portionside wall guide surface bushing guide surface inner piston shoulder annular bushing shoulder proximal sliding surface distal sliding surface axial sealing interface bushing hole piston groove axial sealing interface first bushing abutment surface second bushing abutment surface annular bushing groove annular bushing gasket annular actuator body groove annular actuator body gasket annular bushing seat annular abutment edge actuator body groove annular actuator gasket motor shaft first planetary gear stage first stage ring gear first stage planet gears first stage planet carrier first stage sun gear first stage pins second planetary gear stage sun-planetary interface second stage sun gear second stage planet gears second stage ring gear second stage planet carrier second stage pins69 rotation pin70 transmission bearing80 planet-rotating member interface100 braking device or brake caliper101 thrust device102 friction element103 braking surface104 braking device body or caliper body105 thrust housing106 inlet opening107 outlet openingX piston axisX-X thrust directionA-A thrust direction or axial directionT-T tangential directionR-R radial directionA0 rest positionA1 thrust positionR lever rotation axis

Claims

CLAIMS1. A thrust actuator (1) for a braking device (100), for example a brake caliper, wherein the braking device (100) comprises a thrust device (101), for example a brake caliper piston, configured to translationally actuate a friction element (102) against a braking surface (103) for braking a vehicle, wherein the braking device (100) comprises a lever (5), wherein the lever (5) is rotationally movable about a rotation axis (R) parallel to a tangential direction (T-T), wherein the lever (5) comprises a lever head (6) integrally rotationally movable at one end of the lever (5), wherein the lever head (6) is configured to receive a thrust force, wherein the lever (5) is mechanically connected to the thrust device (101) so that by rotating actuates in translation the thrust device (101) for translationally actuating the friction element (102) for braking the vehicle, wherein the thrust actuator (1) comprises- a piston (3), wherein the piston (3) comprises a thrust head (4), wherein the thrust head (4) is configured to transfer, either directly or indirectly, the thrust force to the lever head (6), wherein the piston (3) has a piston axis (X),- a transformation assembly (21), wherein the transformation assembly (21) comprises a rotating member (22) and a thrust member (23), wherein the thrust member (23) is mechanically coupled to the piston (3), wherein the rotating member (22) is mechanically coupled to the thrust member (23) so as to transform a rotation of the rotating member (22) into a linear translation of the thrust member (23) which allows a linear reversible displacement along the thrust direction (X-X) of the piston (3), wherein the rotating member (22) is configured to receive a torque from an electric motor (20), either directly or indirectly, by means of a transmission (24), wherein the thrust direction (X-X) of the piston (3) is parallel to an axial direction (A-A) and perpendicular to both the radial direction (R-R) and the tangential direction (T-T),- an actuator body (18) configured to accommodate and support the transformation assembly (21) and the piston (3),wherein the actuator body (18) delimits a housing opening (12), and comprises at least one housing side wall (13) and at least one housing shoulder (11), wherein the at least one housing side wall (13) extends at least from the at least one housing shoulder (11) to the housing opening (12) delimiting a housing (19) configured to house the transformation assembly (21) and the piston (3), wherein the piston (3) is housed in the housing (19) translationally movably along the thrust direction (X-X) between a rest position (AO) to a thrust position (A1) reversibly projecting the thrust head (4) from the housing opening (12) by actuating the electric motor (20), a detection sensor (9), wherein the detection sensor (9) is connected to the actuator body (18) and arranged axially downstream of the transformation assembly (21) on the side opposite to the housing opening (12) so as to detect, either directly or indirectly, a reaction force opposite to the thrust force (FA) discharged from the piston (3) to the transformation assembly (21), characterized in that thrust actuator (1) comprises- a bushing (17), wherein the bushing (17) is constrained to the actuator body (18) at the housing opening (12), wherein the bushing (17) is coupled to the piston (3) by constraining the thrust head (4) to translate in a direction parallel to the piston axis (X) and preventing the piston (3) from oscillating about directions incident or perpendicular to the piston axis (X), wherein the bushing (17) is configured to translationally support the piston (3) by discharging onto the bushing (17) any radial component of the thrust force with respect to the thrust direction (X-X) and avoiding misalignment of the piston (3) inside the housing (19).

2. A thrust actuator (1) according to the preceding claim, wherein the bushing (17) comprises at least one bushing guide surface (35), wherein the piston (3) comprises a proximal piston portion (14) and a distal piston portion (15), wherein the proximal piston portion (14) is connected to the transformation assembly (21) and delimits a piston cavity (16) for accommodating, at least partially, the transformation assembly (21),wherein the distal piston portion (15) is connected to the thrust head (4) or comprises the thrust head (4), wherein the distal piston portion (15) comprises at least one distal sliding surface (39), wherein each distal sliding surface (39) translationally slides in contact with a respective surface of the at least one bushing guide surface (35) so as to translationally support the piston (3) by discharging onto the bushing (17) radial components of the thrust force with respect to the thrust direction (X-X) and avoiding misalignment of the piston (3) inside the housing (19).

3. Thrust actuator (1) according to the preceding claim, wherein the at least one housing side wall (13) comprises at least one side wall guide surface (34), wherein the piston (3) is a stepped piston, wherein the proximal piston portion (14) is connected to the distal piston portion (15) by reducing the diameter of the piston (3), wherein the proximal piston portion (14) comprises at least one proximal sliding surface (38), wherein each proximal sliding surface (38) translationally slides in contact with a respective one of the at least one side wall guide surface (34) avoiding a rotation of the piston (3) about the thrust direction (X-X), wherein the piston (3) is slidingly guided and supported by at least two zones having different diameters, wherein the piston (3) is guided by the bushing guide surface (35) of the bushing (17) and by the at least one side wall guide surface (34), wherein the bushing guide surface (35) extends at least partially within the housing (19) on the side axially opposite to the housing opening (12), wherein the bushing guide surface (35) is interposed between the distal piston portion (15) and the at least one side wall guide surface (34) along which the proximal piston portion (14) is slidable.

4. A thrust actuator (1) according to claim 2, wherein the bushing (17) is coupled to the distal piston portion (15) in a sliding sealing manner,avoiding dust or humidity from entering the housing (19) from the outside, wherein the bushing (17) comprises a bushing hole (41), wherein the bushing hole (41) is coaxial to the thrust direction (X-X), wherein the at least one bushing guide surface (35) delimits the bushing hole (41), wherein the at least one distal sliding surface (39) delimits the distal piston portion (15) radially with respect to the thrust direction (X-X), wherein the at least one bushing guide surface (35) and the at least one distal sliding surface (39) are counter-shaped with respect to each other so as to sealingly slide over each other with low friction.

5. A thrust actuator (1) according to any one of claims 2 to 4, wherein the proximal piston portion (14) is mechanically coupled to the at least one housing side wall (13) forming an anti-rotational constraint which prevents the piston (3) from rotating about the thrust direction (X-X), for example wherein the proximal piston portion (14) and the at least one housing side wall (13) are counter-shaped so as to geometrically prevent the piston (3) from rotating in the housing (19) and / or wherein the proximal piston portion (14) has a piston groove (42) parallel to the axial direction (A-A) and the thrust actuator (1) comprises an anti-rotation pin (25) connected to the actuator body (18) projecting from the at least one housing side wall (13) so as to mechanically couple to the piston groove (42) preventing the piston (3) from rotating about the thrust direction (X-X).

6. A thrust actuator (1) according to any one of the preceding claims, comprising a thrust bearing (10), wherein the thrust bearing (10) rotationally supports the rotating member (22), wherein the detection sensor (9) is arranged between the thrust bearing (10) and the housing shoulder (11), for detecting the reaction force, opposite to the thrust force, discharged from the piston (3) to the transformation assembly (21), preferably wherein the detection sensor (9) is a force sensor, for example configured to elastically deform generating a signal which is transmitted to a control unit by means of a sensor interconnector (30), wherein the sensor interconnector (30) is connected to theactuator body (18).

7. A thrust actuator (1) according to any one of the preceding claims, wherein the transformation assembly (21) is a screw-nut assembly, preferably of the recirculating ball type, preferably wherein the thrust member (23) comprises a nut, wherein the rotating member (22) comprises a worm screw.

8. A thrust actuator (1) according to claim 2 and claims 6 and 7, wherein the piston cavity (16) is a stepped cavity and comprises a proximal cavity portion (31) made in the proximal piston portion (14) and a distal cavity portion (32) made partially in the distal piston portion (15), wherein the piston (3) comprises an inner piston shoulder (36) axially between the proximal cavity portion (31) and the distal cavity portion (32), preferably wherein the piston cavity (16) is closed on the side of the thrust head (4) and open on the axially opposite side, wherein the thrust member (23) is housed in the proximal cavity portion (31) and constrained to the proximal piston portion (14), preferably wherein the actuator (1) comprises a thrust ring (26), wherein the thrust ring (26) is axially arranged between the thrust member (23) and the inner piston shoulder (36), wherein the rotating member (22) is constrained to the thrust bearing (10).

9. A thrust actuator (1) according to any one of the preceding claims, wherein the bushing (17) is a sliding bushing, wherein each bushing guide surface (35) is self-lubricating, and / or wherein the bushing (17) comprises a matrix made of sintered material and lubricant particles trapped in the matrix made of sintered material, so that each bushing guide surface (35) is constantly lubricated reducing friction during the sliding of the piston (3) through the bushing (17).

10. Thrust actuator (1) according to any one of the preceding claims, wherein the bushing (17) comprises an axial sealing interface (43) configured to axially abut against abraking device body (104) of the braking device (100) so as to connect the thrust actuator (1) to the braking device (100) in a fluid-tight manner.

11. Thrust actuator (1) according to any one of the preceding claims, wherein the bushing (17) comprises an annular bushing body delimiting a bushing hole (41) and an annular bushing shoulder (37) radially projecting from the annular bushing body on the side opposite to the bushing hole (41), wherein the annular bushing shoulder (37) comprises a first bushing abutment surface (44) configured to abut against the actuator body (18), wherein the annular bushing body comprises a cantilevered portion projecting from the annular bushing shoulder (37) axially on the side opposite to the housing opening (12), inserting into the housing (19) in contact with the at least one housing side wall (13) and / or with the at least one side wall guide surface (34).

12. Thrust actuator (1) according to any one of the preceding claims 10 to 11, wherein the annular bushing shoulder (37) comprises a second bushing abutment surface (45) on the side axially opposite to the first bushing abutment surface (44), wherein the second bushing abutment surface (45) delimits an annular bushing groove (46), wherein the bushing (17) and / or the actuator (1) comprises an annular bushing gasket (47), for example an O-ring, wherein the annular bushing gasket (47) is housed in the annular bushing groove (46), wherein the axial sealing interface (43) comprises the second bushing abutment surface (45) and the annular bushing gasket (47).

13. Thrust actuator (1) according to any one of the preceding claims 10 to 12, wherein the actuator body (18) comprises an annular bushing seat (50) configured to house the annular bushing shoulder (37) axially abutting against the second bushing abutment surface (45), wherein the actuator body (18) comprises an annular abutment edge (51), arranged radially outsidewith respect to the annular bushing seat (50), wherein the annular abutment edge (51) is configured to axially abut against the braking device body (104) of the braking device (100) so as to connect the thrust actuator (1) to the braking device (100) in a fluid-tight manner, in two distinct zones both via the bushing and via the actuator body, wherein the annular abutment edge (51) comprises an actuator body groove (52), wherein the actuator (1) comprises an annular actuator gasket (53), for example an O-ring, wherein the annular actuator gasket (53) is housed in the actuator body groove (52).14 Thrust actuator (1) according to any one of the preceding claims, comprising an electric motor (20) comprising a respective motor shaft (55), and a transmission (24), wherein each motor shaft (54) is connected to the transmission (24), wherein the transmission (24) is connected to the rotating member (22) so as to transfer the rotation of the at least one motor shaft (55), reduced by the transmission (24), to the rotating member (22).

15. Thrust actuator (1) according to any one of the preceding claims, wherein the braking device (100) is an electromechanically actuated brake caliper, wherein the thrust actuator (1) comprises an electric motor (20) so as to electromechanically actuate a thrust device (101) of the brake caliper.

16. Thrust actuator (1) according to any one of the preceding claims, wherein the braking device (100) is a brake caliper for heavy vehicles, for example trucks, road trains, articulated lorries.

17. Braking device (100), for example a brake caliper, comprising- a braking device body (101), for example a caliper body, wherein the braking device body (104) delimits a thrust housing (105) between an inlet opening (106) and an outlet opening (107),- a lever (5), wherein the lever (5) is connected to the braking device body (101) and is housed in the thrust housing (105), wherein the lever (5) is rotationally movable about a rotation axis (R) parallel toor coincident with a tangential direction (T-T), wherein the tangential direction (T-T) is perpendicular to a direction parallel to a thrust direction (A-A), wherein the lever (5) comprises a lever head (6) integrally rotationally movable at one end of the lever (5),- a thrust device (101), wherein the thrust device (101) is housed in the thrust housing (105), wherein the thrust device (101) is configured to translationally actuate a friction element (102) against a braking surface (103) for braking a vehicle, protruding from the outlet opening (107),- a thrust actuator (1) according to any one of the preceding claims, wherein the actuator body (18) is connected to and supported by the braking device body (104), wherein the housing opening (12) faces the inlet opening (106) so that the thrust head (4) is translationally movable into the thrust housing (105), wherein the thrust head (4) is configured to abut, either directly or indirectly, with the lever head (6) so as to transform the translation of the piston (3) into the rotation of the lever (5), wherein the lever (5) is mechanically connected to the thrust device (101) so that, by rotating, it translationally actuates the thrust device (101) to translationally actuate the friction element (102) to brake the vehicle.

18. Braking device (100) according to the preceding claim, wherein the braking device (100) is an electromechanically actuated brake caliper, wherein the thrust actuator (1) comprises an electric motor (20) so as to actuate the thrust device (101) via the lever (5) to actuate the brake caliper electromechanically.

19. Braking device (100) according to any one of the preceding claims 14 to 15, wherein the braking device (100) is a brake caliper for heavy vehicles, for example trucks, road trains, articulated lorries.

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