Actuating device for disc brake

Abstract

An actuator device (1) for a disc brake (2) comprises a piston (7), a first ball-in-ramp motion converter (100), having a first ramp portion (101) axially constrained and rotatable around the actuation axis (8), a second ramp portion (102) coupled with the piston (7), and a plurality of rolling elements (29) interposed in contact between ramp tracks (103) formed by the first (101 ) and second ramp portions (102), a second motion converter (4) of screw and nut type, connected between the second ramp portion (102) and the piston (7), a torque limiter (10) which provides a torsional connection between the first ramp portion (101) and the second ramp portion (102), allowing their rotation in unison around the actuation axis (8) until a predetermined torque threshold is reached in said torsional connection, and decoupling the rotation of the first ramp portion (101) relative to the second ramp portion (102) around the actuation axis (8) upon exceeding the predetermined torque threshold, as well as a position sensor (64) configured to detect a position of the second ramp portion (102) and to generate a detected position signal of the second ramp portion (102).

Description

“ACTUATING DEVICE FOR DISC BRAKE”

[0001] The present invention relates to an actuating device for a disc brake, in particular for an electromechanical disc brake, equipped with an electronic control system for actuation control of the brake, as well as to a disc brake provided with such actuating device.

[0002] Electrically controlled disc brakes are known, in particular electromechanical disc brakes with one or more pistons supported in a brake caliper and movable into engagement against a brake disc by means of an electric motor and a transmission interposed between the electric motor and the respective piston. The electric motor is controlled by an electronic control system having a force sensor mounted on the disc brake and configured to detect a force acting on the piston or on the transmission and to generate a corresponding force signal. The electronic control system controls the electric motor by means of a control algorithm depending at least also on the detected force signal.

[0003] Depending on the control algorithm implemented by the control system, the force signal can be used as representative of a force or pressure or generic stress acting on the brake disc, on the piston or on the transmission, that is, a confirmation of the actual effect detected of the motor actuation, essential to close the loop, e.g. PID, of the control algorithm.

[0004] Actuating devices for disc brakes are known, comprising a geared motor associated with a recirculating ball screw or with a screw and nut transmission, which transforms the torque generated by the geared motor into an axial force acting on the piston to move the piston axially towards the brake disc.

[0005] A further known type of transmission is the so-called “ball-in-ramp” mechanism. A ballin-ramp mechanism is also a motion converter from rotary motion to translational motion and comprises two facing components, rotatable relative to each other, and a plurality of balls interposed in contact between the two facing components and housed within rolling tracks (or ramps) formed in the two components. The rolling tracks have a helical development so that the relative rotation between the two facing components determines a wedge effect and an axial translation thereof with mutual separation.

[0006] Ball-in-ramp mechanisms have axial dimensions much smaller than recirculating ball screws, are capable of generating very high braking forces depending linearly or non-linearly (depending on the configuration of the ramp tracks for the balls) on the relative rotation angle of the two facing components.

[0007] However, known ball-in-ramp mechanisms have the drawback of a very limited axial stroke, which makes it difficult to compensate for brake pad wear.

[0008] Actuating devices for disc brakes have therefore been developed that combine a screw and nut mechanism, or alternatively a recirculating ball screw, with a ball-in-ramp mechanism, so as to implement two distinct transmission stages or conditions, a first transmission stage (activating the screw - nut mechanism) to advance and / or retract the piston and compensatethe extra stroke of the piston due to pad wear, and a second stage (activating the ball-in-ramp mechanism) to transmit braking force to the disc brake pad, such that the pad generates a braking torque on the brake disc.

[0009] The force sensors used in electromechanical brakes of known technology are more expensive than some other types of sensors and, if possible, it would be desirable to eliminate the force sensors, reduce their cost, or replace them with more economical detectors.

[0010] Furthermore, force sensors have dimensions and constraints of positioning and accessibility such as to make their integration into the body of the brake caliper complex and costly.

[0011] Moreover, in the case of two-speed transmissions, in particular transmissions with a slower first transmission stage, typically a screw and nut transmission, and a faster second transmission stage, typically a ball-in-ramp transmission, or vice versa, the variation in the ratio between the piston displacement speed and the rotation speed of the electric motor rotor (pitch difference) makes the interpretation of the force signal and the control of the braking system more difficult and uncertain. A further difficulty lies in the challenge of unambiguously correlating the number of revolutions or the angular position of the motor rotor to the position of the piston (a problem that does not exist in the case of a recirculating ball screw).

[0012] There is therefore a need to know at each moment in time in which phase or transmission stage (screw-nut or ball-in-ramp) the kinematic system is, in order to be able to determine more precisely the axial position of the piston as a function of the (cumulative) angular position of the electric motor rotor.

[0013] The aim of the present invention is therefore to provide an actuating device for a disc brake, and an electromechanical disc brake, having characteristics such as to overcome at least some of the drawbacks of the prior art.

[0014] A particular aim of the present invention is to reduce the costs and complexity of integrating a sensor into the disc brake.

[0015] A further particular aim of the present invention is to provide an actuating device for a disc brake, and a disc brake, usable with sensors other than force sensors and versatile for the use of different types of sensors.

[0016] At least some of the aims are achieved by means of an actuating device for a disc brake according to claim 1 .

[0017] The dependent claims relate to preferred and advantageous embodiments of the present invention.

[0018] To better understand the invention and appreciate its advantages, some exemplary and non-limiting embodiments will be described below, with reference to the attached figures, in which:

[0019] - Figure 1 is a perspective view of a disc brake, according to one embodiment of theinvention;

[0020] - Figure 2 is a sectional view in a radial plane of a detail of a disc brake, according to one embodiment of the invention;

[0021] - Figure 3 is an exploded view of an actuating device for a disc brake, according to one embodiment of the invention;

[0022] - Figure 4A is a perspective view of a partially assembled actuating device for a disc brake, according to one embodiment of the invention;

[0023] - Figure 4B is a perspective view of the actuating device for a disc brake of figure 4A, assembled;

[0024] - Figure 5 is a radial sectional view of the actuating device of figure 4B;

[0025] - Figure 5A is a detailed view of an actuating device, according to one embodiment of the invention;

[0026] - Figure 5B is an exploded view of a detail of the actuating device, according to an alternative embodiment with respect to figure 3;

[0027] - View 6A is a sectional view orthogonal to a drive axis, in a first operating configuration;

[0028] - View 6B is a sectional view orthogonal to a drive axis, in a second operating configuration;

[0029] - Figure 7A is a schematic view of a detail of a disc brake indicating the position of a position sensor, according to one embodiment;

[0030] - Figure 7B is a schematic view of a detail of a disc brake indicating the position of a position sensor, according to a further embodiment;

[0031] - Figure 8 is an exploded view of an actuating device for a disc brake, according to another embodiment of the invention;

[0032] - Figure 8A is another exploded view of the actuating device for a disc brake shown in figure 8;

[0033] - Figure 9 is a perspective view of a partially assembled actuating device for a disc brake, according to another embodiment of the invention;

[0034] - Figure 10 is a radial sectional view of the actuating device of figure 9, assembled;

[0035] - Figure 10A is a radial sectional view of an actuating device for a disc brake, according to one embodiment of the invention;

[0036] - Figure 1 1 A is a perspective view of a partially assembled actuating device for a disc brake, according to one embodiment of the invention;

[0037] - Figure 11 B is a perspective view of the actuating device for a disc brake of figure 1 1A, assembled;

[0038] - Figure 12 is a radial sectional view of an actuating device of a disc brake, according to a further embodiment;

[0039] - Figure 13A is a perspective view of an actuating device, according to anotherembodiment of the invention;

[0040] - Figure 13B is a front view of the actuating device in figure 13A;

[0041] - Figure 14A is a schematic view of a detail of a disc brake indicating the position of a position sensor, according to one embodiment;

[0042] - Figure 14B is a schematic view of a detail of a disc brake indicating the position of a position sensor, according to a further embodiment.

[0043] Detailed description of the invention

[0044] In the following description, the orientation term “front” refers to the orientation of sides, faces, surfaces, etc., in the direction of advancement (braking) of the piston; the orientation term “rear” refers to the orientation of sides, faces, surfaces, etc., in the direction of retraction of the piston, unless otherwise specified. The terms “radial”, “circumferential”, and “axial” are to be understood with respect to the actuation axis of the piston, unless otherwise specified.

[0045] With reference to the figures, an actuating device 1 for a disc brake 2 comprises:

[0046] - a piston 7 slidably supported along an actuation axis 8,

[0047] - a first ball ramp motion converter 100, having a first ramp portion 101 axially stationary and rotatable about the actuation axis 8, a second ramp portion 102 coupled with the piston and facing the first ramp portion 101 , and a plurality of rolling elements (balls) 29 interposed in contact between ramp tracks 103 formed by the first 101 and second 102 ramp portions, so that the rotation of the first ramp portion 101 with respect to the second ramp portion 102 results in a braking translation of the second ramp portion 102 together with the piston 7 with respect to the first ramp portion 101 , along the actuation axis 8,

[0048] - a second motion converter 4 of the screw and nut type without recirculating balls, connected between the second ramp portion 102 and the piston 7, so that a rotation of the second ramp portion 102 with respect to the piston 7 about the actuation axis 8 results in a further compensating translation of the piston 7 with respect to the second ramp portion 102, along the actuation axis 8,

[0049] - a torque limiter 10 (or, in other words, a torsional clutch) that:- creates a torsional connection of the first ramp portion 101 with the second ramp portion 102, for their unison rotation about the actuation axis 8 until a predetermined limit torque in said torsional connection is reached,- decouples the rotation of the first ramp portion 101 with respect to the second ramp portion 102 about the actuation axis 8 when the predetermined limit torque is exceeded.

[0050] In this manner, in a first step of approach of the piston 7 toward the brake pad until piston-pad-brake disc engagement (the extra stroke phase necessary to compensate for worn pad thickness), both ramp portions 101 , 102 of the first ball-in-ramp motion converter 100 rotate in unison and advance the piston 7, by virtue of the action of the second screw-and-nut motion converter 4 alone.

[0051] At the end of the first approach step, the compressive engagement between piston, pad and brake disc increases the mechanical resistance against further advancement of the piston 7 until the predetermined limit torque in the torsional connection between the first ramp portion 101 and the second ramp portion 102 is exceeded, and their relative rotation causes the braking translation of the piston 7 (over a very limited braking stroke), by virtue of the action of the first ball-in-ramp motion converter 100 alone.

[0052] The first ramp portion 101 may be connected to an input shaft or to a generic rotary input member 3, for example of a reduction gear or of an electric motor.

[0053] In a conventional manner, the piston 7 is configured to transmit an axial force in the direction of the actuation axis 8 to a brake pad 9 of the disc brake 2.

[0054] The actuating device 1 configured in this manner converts a torque coming from the rotary input member 3 into a linear force through two distinct operating steps. In the first step, wear compensation of the brake pads 9 of the disc brake 2 is performed, by moving the piston 7 toward the brake pad 9 of the disc brake 2. This movement is achieved by means of the second screw-and-nut motion converter 4, through forces that are not high and are lower than the braking force. In the second step, the actual braking takes place, i.e. the generation of the braking force by the piston 7 on the brake pad 9 of the disc brake 2. The translational movement of the piston 7 that generates the braking force is produced by means of the first ball-in-ramp motion converter 100.

[0055] According to one aspect of the invention, the actuating device 1 comprises a position sensor 64 mounted in a stationary manner with respect to a generic support structure or, more specifically, to the brake caliper 52, and configured to detect:

[0056] - a translational position of the second ramp portion 102 along the actuation axis 8, and / or

[0057] - an angular position of the second ramp portion 102 about the actuation axis 8,

[0058] and to generate a detected-position signal of the second ramp portion 102.

[0059] This makes it possible to avoid the use of costly force sensors, replacing them with more economical position sensors. To this end, the control algorithm implemented by the control system 54 of the disc brake 2 is adapted so as to use the detected position signal as a feedback signal for a control loop and for regulating the supply of the electric motor 53.

[0060] The position sensor, which provides the instantaneous position of the second ramp portion 102 (a component that is rotating but translationally stationary until the moment of piston-pad-disc contact, and translationally moving only from the moment of piston-pad-disc contact), allows the control system 54 to determine the position, displacement, and possibly also the displacement speed of the piston 7, as well as the exact moment at which pad-disc contact occurs.

[0061] Position detection is typically simpler than force detection and can be carried out frommultiple different positions, including in contactless mode, making integration of the sensor 64 into the brake caliper body 52 simpler and more economical.

[0062] Moreover, in the case of two-speed transmissions, with one screw-and-nut transmission stage and a second ball-in-ramp transmission stage, detection of the position of the second ramp portion 102 allows determining with certainty whether the system is in one or the other of the two different transmission stages, and enables more precise determination of the piston position and of the load applied to the brake disc 49, thereby allowing more accurate control and regulation of the braking system.

[0063] The position sensor 64 may be positioned with a detection field orientation in a radial direction with respect to the actuation axis 8 and configured to detect an axial translational position of the second ramp portion 102 along the actuation axis 8.

[0064] Alternatively, the position sensor 64 is positioned with a detection field orientation in a radial direction with respect to the actuation axis 8 and configured to detect an angular, rotary position of the second ramp portion 102 about the actuation axis 8.

[0065] Alternatively, the position sensor 64 is positioned with a detection field orientation in a direction parallel or coaxial with respect to the actuation axis 8 and configured to detect an axial translational position of the second ramp portion 102 along the actuation axis 8.

[0066] Alternatively, the position sensor 64 is positioned with a detection field orientation in a direction parallel or coaxial with respect to the actuation axis 8 and configured to detect an angular, rotary position of the second ramp portion 102 about the actuation axis 8.

[0067] In fact, since position detection of a mechanical component is much easier than force detection (as in the prior art), and since the actuating device 1 inherently already provides a component — namely the second ramp portion 102 — that undergoes both rotational and translational movement and therefore allows unequivocal distinction between the two different movement stages of the transmission and of the piston, the sensor 64 itself can be easily fixed to the brake caliper 52 in the most suitable position.

[0068] According to one embodiment, the position sensor 64 detects the position of the second ramp portion 102 with respect to a reference position on the support structure or brake caliper 52 or on the first ramp portion 101.

[0069] The position sensor 64 is preferably screwed to or into the support structure or brake caliper 52 and has signal contact terminals for a wired transmission of the detected position signal.

[0070] According to one embodiment, the actuating device 1 or the disc brake 2 comprises an electronic control unit 55 (which may be part of the electronic control system 54 of the disc brake 2), with its own hermetically sealed housing 56, screwed to the support structure or brake caliper 52, in which the position sensor 64 is fixed and at least partially embedded in the polymer material of the housing 56, by injection molding. This allows integration of all electroniccomponents located near the disc brake 2, including the feedback sensor (i.e. the position sensor 64), in a single sealed housing 56 that can be mounted / dismounted as a single module, a particularly advantageous condition for applications in motorcycles with limited space.

[0071] The position sensor 64 may comprise one or more of: a Hall effect sensor, magnetic sensor, capacitive sensor, LVDT (linear variable displacement transducer) sensor, available as very reliable and low-cost commercial components.

[0072] Detailed description of the first ball-in-ramp motion converter 100

[0073] According to one embodiment, the first ramp portion 101 may itself form the rotary input member 3 of the device 1 , and the second ramp portion 102 may be directly formed on a screw body 5 of the second screw-and-nut motion converter 4.

[0074] This increases the compactness of the actuating device 1 , reducing its size along the actuation axis 8.

[0075] According to an advantageous embodiment, the first ramp portion 101 is formed by a rotor body 23 having a substantially cylindrical shape, with a circumferential rotor wall 25 extending along the actuation axis 8, a front rotor wall 26, and a rear rotor wall 27.

[0076] The front rotor wall 26 faces in the direction of advancement of the piston 7 and forms one or more, preferably three, first rolling tracks 28 of the ramp tracks 103, as well as a drive shaft 24 protruding from the front rotor wall 26, coaxial to the actuation axis 8, and connected to the torque limiter 10. The drive shaft 24 may also form a rotary support and centering element for the second ramp portion 102.

[0077] The circumferential rotor wall 25 may form a gear toothing 50 extending around the actuation axis 8, for example at the rear rotor wall 27, for transmission of a drive torque / rotation.

[0078] According to an alternative embodiment (figure 12), the rotor body 23 is formed as a radial enlargement of a shaft 48 that forms both the drive shaft 24 extending axially within the actuating device 1 , and an input shaft extending on a rear side of the rotor body 23 opposite the drive shaft 24.

[0079] According to one embodiment, the first motion converter 100 comprises a bearing assembly 105 configured for positioning the first ramp portion 101 , in particular the rotor body 23, in a translationally stationary and concentrically aligned position with respect to the actuation axis 8, and to support the axial loads generated during operation of the actuating device 1 and, possibly, also the radial loads due to meshing with the gear teeth 50.

[0080] Advantageously, the bearing assembly 105 is positioned inside the rotor body 23, coaxial with the rotor body 23 and, possibly, in the area of the gear teeth 50 (to directly provide radial reaction support).

[0081] The bearing assembly 105 may comprise a four-contact point rolling bearing.

[0082] According to one embodiment, a rear screw wall 21 of the screw body 5, facing the rotor body 23, forms at least one, preferably three, second rolling tracks 22 of the cam tracks103.

[0083] Advantageously, a first rolling track 28 and a second rolling track 22 facing each other respectively accommodate a rolling ball 29 between them.

[0084] The ramp tracks 103 of the ramp portions 101 , 102 extend helically (or, in other words: eccentrically and in a circumferential direction) with respect to the actuation axis 8. Each of the ramp portions 101 , 102 may form, for example, two or three rolling tracks 103 arranged in circumferential succession and separated by dividing ribs so as to accommodate the rolling members (balls) 29 in their planned position.

[0085] The ramp tracks 103 may be configured as variable-pitch helices in the direction of the actuation axis 8, defining a non-linear rotation-to-translation conversion law.

[0086] According to one embodiment, at least one ramp track 103 is shaped to radially limit the movement of the ball 29.

[0087] Advantageously, this prevents the risk of any accidental ejection of the at least one ball 29 from the corresponding ramp track 103.

[0088] According to one embodiment, the rolling balls 29 are further accommodated by a containment cage 30 interposed between the first ramp portion 101 and the second ramp portion 102, or between the rotor body 23 and the screw body 5, advantageously supported (rotatably) on the drive shaft 24.

[0089] According to one embodiment, the containment cage 30 forms vanes 104 or ball seats that are radially open or closed and encasing, to prevent radial ejection of the rolling balls 29.

[0090] According to one embodiment, the first ramp portion 101 , the second ramp portion 102, and the rolling members (balls) 29 are elastically pressed into contact with each other in the direction of the actuation axis 8.

[0091] This prevents the onset of vibrations of the balls within the ramp tracks and noise, and keeps the individual components in their planned position.

[0092] According to one embodiment (figures 1 1 A, 11 B), the actuating device 1 comprises an axial preload spring 42, configured to axially push the first ramp portion 101 toward the second ramp portion 102, or in other words, the screw body 5 against the rotor body 23. The same axial preload spring 42 may be arranged to axially preload the entire assembly of the first motion converter 100 and the torque limiter 10.

[0093] The axial preload spring 42 may be supported (for example, via a Seeger ring 41 ) on the drive shaft 24 and clamped between a free end portion (front, facing the direction of advancement of the piston 7) of the drive shaft 24 and a front wall 20 of the screw body 5, such as a helical spring, one or more Belleville springs in series, or a wave spring.

[0094] According to one embodiment (figures 10, 10A), the drive shaft 24 (formed as a single piece or integral with the rotor body 23) forms an axial through-hole that houses a tie rod 46 having a front end with a mushroom or disk-shaped head axially resting against the front wall20 of the screw body 5 (in the direction opposite to the advancement direction of the piston 7) and a rear end portion protruding into an internal cavity of the rotor body 23, in which an axial preload spring 42’, advantageously a Belleville spring, or multiple Belleville springs in series, or one or more helical springs inserted on the tie rod 46, may be supported (for example, by means of a Seeger ring 41 ’) on the tie rod 46 and clamped between the rear end portion of the tie rod 46 and a bottom surface of the internal cavity of the rotor body 23, preferably via the interposition of an axial (rolling) bearing 47.

[0095] According to one embodiment, the position sensor 64 is positioned on a rear side of the actuating device 1 opposite a front side intended to face the brake disc 49, and oriented coaxially with respect to the actuation axis 8. An air gap is formed between the rear end portion of the tie rod 46 and the position sensor 64. The tie rod 46 is integral with the second ramp portion 102, and the position sensor detects the position of the second ramp portion 102 by detecting the position of the rear end portion of the tie rod 46. If an LVDT (linear variable displacement transducer) is used as the position sensor 64, the aforementioned air gap will not be present, but rather a contact between the end of the tie rod 46 and an end of the LVDT sensor 64.

[0096] According to one embodiment, the position sensor 64 forms an external thread 57 screwed into a corresponding internal thread 58 of the support structure or brake caliper 52, said internal thread 58 being coaxial with the actuation axis 8.

[0097] Advantageously, the first motion converter 100, the second motion converter 4, and the torque limiter 10 are at least partially, preferably completely, accommodated within an internal cavity of the piston 7, thus occupying the same axial space.

[0098] With further advantage, the torque limiter 10 is at least partially, preferably completely, housed in an internal cavity of the second screw-and-nut motion converter 4, preferably in an internal cavity of the screw body 5, thus occupying the same axial space.

[0099] Detailed description of the piston 7 and the second screw-and-nut motion converter 4

[0100] According to one embodiment, the piston 7 has a substantially hollow cylindrical shape concentric with the actuation axis 8, with a cylindrical wall 14 defining an external piston surface 1 1 and an internal piston surface 12, and a head wall 13 transverse to the lateral wall 14 and formed at a front end of the piston 7 and, in operating conditions, facing the brake pad 9 of the disc brake 2.

[0101] According to one embodiment, the internal piston surface 12 is threaded and screwed onto the screw body 5 so as to form a nut screw 6 of the second screw-and-nut motion converter 4.

[0102] According to one embodiment, the piston 7 forms anti-rotation means, for example one or more radial projections 16 slidably accommodated in one or more corresponding guides 16’ formed in the cylinder 16” and extending in the direction of the actuation axis 8, so as toallow axial translation and prevent rotation of the piston 7 relative to the cylinder 16”.

[0103] In accordance with one embodiment, the projection 16 may be formed by a grub screw, preferably made of steel, inserted or screwed into a (threaded) hole 15 of the cylindrical wall 14, and oriented radially with respect to the actuation axis 8.

[0104] By preventing rotation of the piston 7 about the actuation axis 8 and translation of the screw 5 along the actuation axis 8, a rotation of the screw body 5 screwed into the internal thread of the piston 7 results in a translation of the piston 7 along the actuation axis 8.

[0105] According to one embodiment, the cylindrical wall 14 may form, on the side of the head wall 13, a circumferential groove 17 suitable for accommodating a dust seal.

[0106] According to one embodiment, the screw body 5 forms:

[0107] - a cylindrical lateral wall 18, concentric with respect to the actuation axis 8, with an external thread for screwing into the internal thread of the piston 7;

[0108] - a front screw wall 20 facing in the direction of advancement of the piston 7, and a rear screw wall 21 opposite the front screw wall 20;

[0109] - a coupling seat 19, preferably radially and axially inside the external thread, which houses the torque limiter 10.

[0110] This configuration contributes to a further reduction in the axial dimensions of the device 1 .

[0111] According to one embodiment, the rear screw wall 21 forms a through-hole 43 opening into the coupling seat 19, through which the drive shaft 24 extends into the coupling seat 19.

[0112] The through-hole 43 provides a centered and rotatable support for the screw body 5 relative to the rotor body 23.

[0113] A circumferential edge between the threaded lateral wall 18 and the front screw wall 20 is beveled to facilitate the insertion and screwing of the screw body 5 into the nut screw 6 formed by the piston 7.

[0114] Detailed description of the torque limiter 10

[0115] According to one embodiment, the torque limiter 10 comprises one or more, preferably two, jaws 31 rotatably coupled to the screw body 5 and elastically urged into engagement with the drive shaft 24.

[0116] According to one embodiment, the coupling seat 19 forms two abutment surfaces 44 opposed in a diametrical direction with respect to the actuation axis 8 and two lateral guide surfaces 44’. The jaws 31 (which may be formed as slides) are housed between the lateral guide surfaces 44’, and guided radially with respect to the actuation axis 8. Between the abutment surfaces 44 and the jaws 31 , preloaded elastic elements 32, such as compression springs 33, are arranged.

[0117] The jaws 31 and a torsional engagement portion of the drive shaft 24 are shaped toform an interference fit (with elastic preload) in rotationally locked engagement.

[0118] In particular, the torsional engagement portion of the drive shaft 24 may have two opposite flat and parallel faces 38, while the jaws 31 may form trapezoidal-shaped coupling surfaces 34 facing the drive shaft 24 (figures 8, 8A).

[0119] When the transmitted torque is below the torque limit, the drive shaft 24 is engaged between the jaws 31 , and the jaws 31 rotate jointly with the drive shaft 24.

[0120] When the torque limit is exceeded, the drive shaft 24 spreads the jaws apart against the elastic force of the compression springs 33, allowing relative rotation of the rotor body 23 with respect to the screw body 5.

[0121] The torque limiter 10 thus configured has a simple structure and allows for easy maintenance and replacement of worn jaws 31 , if necessary.

[0122] Advantageously, the torque limiter 10 comprises two jaws 31 positioned opposite each other with respect to the drive shaft 24.

[0123] According to one embodiment, each jaw 31 forms a coupling surface 34 facing the drive shaft 24 and a stress surface 35 against which the elastic element 32 acts to urge the jaw 31 against the drive shaft 24.

[0124] Advantageously, the stress surface 35 forms a seat 40 to accommodate one end of the elastic element 32.

[0125] According to a further embodiment, the coupling surface 34 includes a substantially planar central surface 36 disposed between two walls or containment surfaces 37 extending transversely or inclined with respect to the stress surface 35, such that the coupling surface 34 is shaped as an open trapezoidal or polygonal channel.

[0126] In accordance with one embodiment, the engagement portion of the drive shaft 24 forms two substantially planar contact surfaces 38 disposed between two opposite curved surfaces of cylindrical or ellipsoidal segment shape 39.

[0127] Advantageously, a transition region between the contact surfaces 38 and the curved surfaces 39 of the shaft 24 is rounded (free of internal angles) or chamfered so as to reduce localized contact pressure and, therefore, the wear of the surfaces. This also allows the jaws 31 to be made from a material less hard than the material of the shaft 24.

[0128] In the engaged configuration between the drive shaft 24 and the jaws 31 , the central surface 36 of the jaws 31 is in contact with the corresponding contact surface 38 of the drive shaft 24, and the walls or containment surfaces 37 of the jaws 31 embrace the drive shaft 24 at the location of the curved surfaces 39.

[0129] Accidental axial ejection of the jaws 31 from the coupling seat 19 is prevented by the mushroom-head front end of the tie rod 46 (figure 10) or by the spring 42 (figures 11 A, 11 B) that at least partially blocks the exit path, keeping the jaws 31 within the space between the mushroom head or spring 42 and a stop wall 45 formed inside the screw body 5.

[0130] According to one embodiment (figure 3), the actuator device 1 includes a retaining ring 41 (for example, a Seeger ring in steel) fixed on the drive shaft 24 so as to retain the jaws 31 between the retaining ring 41 and the stop wall 45 of the screw body 5, preventing the jaws 31 from exiting the coupling seat 19.

[0131] According to an alternative embodiment (figures 13A, 13B), the torque limiter 10 includes a torsion spring 51 , such as a spiral spring connected between the first ramp portion 101 and the second ramp portion 102 of the first motion converter 100.

[0132] The torque-deformation curve of the torsion spring 51 is selected such that, below the predetermined torque limit, the flat spiral spring 51 substantially couples in rotation the first ramp portion 101 and the second ramp portion 102, while above the predetermined torque limit, the torsion spring 51 progressively deforms allowing relative rotation of the first ramp portion 101 with respect to the second ramp portion 102.

[0133] According to one embodiment, a first end of the torsion spring 51 is fixedly connected to the rotor body 23, particularly to the drive shaft 24, and the second end of the torsion spring 51 is fixedly connected to the screw body 5.

[0134] According to one non-limiting but exemplary embodiment, the predetermined torque limit may be between 800 Nmm and 400 Nmm, preferably between 690 Nmm and 490 Nmm, even more preferably between 640 Nmm and 540 Nmm, and even more preferably, the predetermined torque limit may be 590 Nmm.

[0135] Advantageously, a predetermined torque limit of this magnitude prevents the onset of instability or irregularities in the braking torque produced by the disc brake 2.

[0136] Description of the disc brake 2

[0137] A disc brake 2 comprises, in a known manner, a caliper 52, including two lateral walls 59, 59’ spaced apart from each other defining a disc space 60 for receiving a portion of a brake disc 49, means for attaching the caliper to a vehicle, a connecting structure 61 that extends across the disc space 60 and connects the lateral walls 59, 59’ to each other, at least one pad seat 62 formed in each of the lateral walls 59, 59’ and configured to receive at least one friction pad 9, thrust means connected to one or both lateral walls 59, 59’ and configured to press the friction pads 9 against the brake disc 49 to clamp it, an electric motor (53) for actuating the thrust means, an electronic control system (54) for controlling the electric motor (53), wherein the thrust means include the actuator device (1 ) with the position sensor (64), and the electronic control system (54) is in signal connection with the position sensor (64) and controls the electric motor (53) based at least also on the detected position signal of the second ramp portion (102).

[0138] Advantageously, the actuator device 1 and / or the disc brake 2 is devoid of a force sensor.

[0001] Advantageously, an actuator device 1 and a disc brake 2 are integrable both in two-wheeled vehicles or motorcycles, both for the front or rear brake, and in motor vehicles and heavy vehicles such as vans and trucks, for example with four wheels or more than four wheels.

[0139] According to one embodiment, the caliper 52 may be of the floating type or, alternatively, a fixed caliper.

Claims

CLAIMS1 . An actuating device (1 ) for brake disc (2), comprising:- a support structure or brake caliper (52),- a piston (7) supported in the support structure or brake caliper (52) in a sliding manner along an actuation axis (8),- a first ball-in-ramp motion converter (100), having a first ramp portion (101 ) axially constrained and rotationally actuatable about the actuation axis (8), a second ramp portion (102) coupled to the piston (7) and facing the first ramp portion (101 ), and a plurality of rolling members (29) interposed in contact between ramp tracks (103) formed by the first (101 ) and second (102) ramp portions, so that the rotation of the first ramp portion (101 ) with respect to the second ramp portion (102) results in a braking translation of the second ramp portion (102) together with the piston (7) with respect to the first ramp portion (101 ), along the actuation axis (8),- a second motion converter (4) with screw and nut screw or recirculating ball screw, connected between the second ramp portion (102) and the piston (7), so that a rotation of the second ramp portion (102) with respect to the piston (7) about the actuation axis (8) results in a compensating translation of the piston (7) with respect to the second ramp portion (102), along the actuation axis (8),- a torque limiter (10) that:- creates a torsional connection of the first ramp portion (101 ) with the second ramp portion (102), for a unison rotation thereof about the actuation axis (8) until a predetermined limit torsional moment in said torsional connection is achieved,- decouples the rotation of the first ramp portion (101 ) with respect to the second ramp portion (102) about the actuation axis (8) when the predetermined limit torsional moment is exceeded, characterized by comprising a position sensor (64) mounted in a stationary manner with respect to the support structure or brake caliper (52) and configured to detect:- a translational position of the second ramp portion (102) along the actuation axis (8), and / or- an angular position of the second ramp portion (102) about the actuation axis (8), and to generate a signal of detected-position of the second ramp portion (102).

2. An actuating device (1 ) according to claim 1 , wherein the position sensor (64) is positioned with an orientation of a detection field in a radial direction with respect to the actuation axis (8) and configured to detect an axial translational position of the second ramp portion (102) along the actuation axis (8).

3. An actuating device (1 ) according to claim 1 , wherein the position sensor (64) is positioned with an orientation of a detection field in a radial direction with respect to the actuation axis (8) and configured to detect an angular, rotary position of the second ramp portion (102) about theactuation axis (8).

4. An actuating device (1 ) according to claim 1 , wherein the position sensor (64) is positioned with an orientation of a detection field in a parallel or coaxial direction with respect to the actuation axis (8) and configured to detect an axial translational position of the second ramp portion (102) along the actuation axis (8).

5. An actuating device (1 ) according to claim 1 , wherein the position sensor (64) is positioned with an orientation of a detection field in a parallel or coaxial direction with respect to the actuation axis (8) and configured to detect an angular, rotary position of the second ramp portion (102) about the actuation axis (8).

6. An actuating device (1 ) according to any one of the preceding claims, wherein the position sensor (64) detects said position of the second ramp portion (102) with respect to a reference position at the support structure or brake caliper (52) or at the first ramp portion (101 ).

7. An actuating device (1 ) according to any one of the preceding claims, wherein the position sensor (64) is screwed to or in the support structure or brake caliper (52) and has signal contact terminals for a wired transmission of the signal of detected position.

8. An actuating device (1 ) according to any one of the preceding claims, comprising an electronic control unit (55) having a hermetically sealed housing (56), screwed to the support structure or brake caliper (52), wherein the position sensor (64) is fixed and at least partially embedded in the polymer material of the housing (56), by injection molding.

9. An actuating device (1 ) according to any one of the preceding claims, wherein the position sensor (64) is selected from the group consisting of:- Hall effect sensor- magnetic sensor- capacitive sensor- LVDT (linear variable displacement transducer) sensor.

10. An actuating device (1 ) according to claim 1 , wherein the second ramp portion (102) is directly formed at a screw body (5) of the second nut and screw motion converter (4), wherein the piston (7) forms:- a cylindrical wall (14) with an internal piston surface (12) threaded and screwed onto the screw body (5) so to form a nut screw (6) of the second motion converter (4) with screw-nutscrew, and- anti-rotation means which prevent the piston (7) from rotating about the actuation axis (8), and wherein the screw body (5) forms:- a cylindrical side wall (18), concentric with respect to the actuation axis (8), with an external thread for screwing with the internal thread of the piston (7),- a front screw wall (20) facing in the direction of advancement of the piston (7) and a rear screw wall (21 ) opposite to the front screw wall (20), said rear screw wall (21 ) forming one or more second rolling tracks (22) of the cam tracks (103),- a coupling seat (19) extending radially and axially inwards with respect to the external thread and which accommodates the torque limiter (10).1 1. An actuating device (1 ) according to any one of the preceding claims, wherein the first ramp portion (101 ) is formed by a rotor body (23) having:- a front rotor wall (26) facing in a direction of advancement of the piston (7) forming one or more first rolling tracks (28) of the ramp tracks (103),- a drive shaft (24) protruding from the front rotor wall (26), coaxial to the actuating shaft (8), and connected to the torque limiter (10), wherein the second ramp portion (102) is rotatably supported and centered on the drive shaft (24).

12. An actuating device (1 ) according to claims 10 and 11 , wherein the rear screw wall (21) forms a through-hole (43) leading into the coupling seat (19), through which the drive shaft (24) extends up to the coupling seat (19), wherein the through-hole (43) forms a centered, rotatable support of the screw body (5) with respect to the rotor body (23).

13. An actuating device (1 ) according to claim 11 , wherein a bearing body (105) supports the rotor body (23) resting axially and concentrically with respect to the actuation axis (8), said bearing assembly (105) being positioned inside the rotor body (23), wherein the rolling members (29) are also accommodated by a containment cage (30) interposed between the first (101 ) ramp portion and second (102) ramp portion and supported on the drive shaft (24).

14. An actuating device (1 ) according to any one of the preceding claims, wherein the first ramp portion (101 ), the second ramp portion (102), and the rolling members (29) are elastically pushed into mutual contact in the direction of the actuation axis (8), wherein the actuating device (1 ) comprises an axial preload spring (42), configured to push the first motion converter (100) and the torque limiter (10) axially together.

15. An actuating device (1 ) according to claims 11 and 12, wherein the drive shaft (24) forms an axial through-hole which accommodates a tie rod (46) having:- an enlarged front end portion, axially resting against a front wall (20) of the screw body (5), and- a rear end portion protruding into an internal cavity of the rotor body (23), wherein an axial preload spring (42') is clamped between the rear end portion of the tie rod (46) and a bottom surface of the internal cavity of the rotor body (23), possibly by means of the interposition of a rolling axial bearing (47).

16. An actuating device (1 ) according to claim 15, wherein the position sensor(64) is positioned on a rear side of the actuating device (1 ) opposite to a front side intended to face the brake disc (49), and oriented coaxially with respect to the actuation axis (8), wherein an air gap is formed between the rear end portion of the tie rod (46) and the position sensor (64), wherein the tie rod (46) is integral with the second ramp portion (102) and the position sensor (64) detects the position of the second ramp portion (102) by detecting the position of the rear end portion of the tie rod (46).

17. An actuating device (1 ) according to claim 16, wherein the position sensor (64) forms an external thread (57) screwed into a corresponding internal thread (58) of the support structure or brake caliper (52), said internal thread (58) being coaxial to the actuation axis (8).

18. An actuating device (1 ) according to any one of the preceding claims, wherein the first motion converter (100), the second motion converter (4), and the torque limiter (10) are at least partially or completely accommodated in an internal cavity of the piston (7), and wherein the torque limiter (10) is at least partially or completely accommodated in an internal cavity of a screw body (5) of the second motion converter (4).

19. An actuating device (1 ) according to any one of the preceding claims, wherein:- the torque limiter (10) comprises one or more jaws (31 ) rotationally integrally coupled to a coupling seat (19) of the second ramp portion (102) and elastically biased to engage a transmission shaft (24) formed at the first ramp portion (101 ),- the coupling seat (19) forms two abutment surfaces (44) opposed to each other in the diametrical direction with respect to the actuation axis (8) and two lateral guide surfaces (44'),- the jaws (31 ) are accommodated between the lateral guide surfaces (44'), and guided radially to the actuation axis (8),- preloaded elastic elements (32) are arranged between the abutment surfaces (44) and thejaws (31 ).

20. An electromechanical disc brake (2) comprising:- a brake caliper (52) having two side walls (59, 59’) spaced apart from each other, which delimit a disc space (60) for accommodating a portion of a brake disc (49), means for fixing the brake caliper (52) to a vehicle, a connection structure (61 ) which extends straddling the disc space (60) and connects the side walls (59, 59’) to each other, at least one pad seat (62) formed in each of said side walls (59, 59’) and adapted to accommodate at least one friction pad (9), thrust means constrained to one or both the side walls (59, 59’) and adapted to bias the friction pads (9) against the brake disc (49) to clamp it,- an electric motor (53) for actuating the thrust means,- an electronic control system (54) for controlling the electric motor (53), characterized in that:- the thrust means comprise the actuating device (1 ) according to any one of the preceding claims,- the electronic control system (54) is in signal connection with the position sensor (64) and controls the electric motor (54) at least also depending on the signal of detected position of the second ramp portion (102).21 . An electromechanical disc brake (2) according to claim 20, having no force sensor.

22. An electromechanical disc brake (2) according to claim 20 or 21 , mounted:- in a motor vehicle or motorcycle with at least two wheels, or- in a motorcar and heavy vehicle with four or more wheels.

Images