FR3077051A1 - NUT DEVICE FORMED BY A SLEEVE AND A METAL WIRE - Google Patents

Abstract

The invention relates to a nut device for a screw-nut mechanism for applying an axial clamping force to a brake piston (50) from a rotary drive within a motorized actuator. . The nut device comprises a wire (20) comprising a wound portion (21) so that it forms a helical winding capable of being wound around an actuated threaded shaft (40). The wire includes a rotational stop portion (25) of the wire radially protruding about said coil (21) to engage pattern engagement with a piston housing (52) to stop rotation of said coil. The nut device includes an actuating sleeve (30) surrounding the wound portion (21) which is inserted into a helical groove of said sleeve. The sleeve comprises an axial bearing face for pressing at least in operation on a rear bearing surface of the brake piston. The field of the invention is that of automotive braking systems.

Description

"Nut device formed by a sleeve and a metal wire"

The invention relates to a nut device for a screw-nut mechanism intended to apply an axial clamping force on a brake piston from a rotary drive, within a motorized actuator.

The nut device comprises a metal wire, a portion of which is wound at a constant diameter so that it forms a helical winding capable of being screwed around a threaded actuating shaft and thus fulfilling a nut function for this shaft. . The metal wire comprises a portion of rotation stop of the wire which protrudes radially around said winding so as to cooperate by engagement of shapes with a housing of the piston to stop the rotation of said winding.

By its external surface, the nut device is designed to be screwed inside in a helical groove of an actuating sleeve, which sleeve comprises an axial bearing face to press at least in operation on a face d rear brake piston support.

The field of the invention is the automotive field and more particularly the screw-nut system of the electric actuators present in the brake assemblies comprising a piston for actuating at least one disc brake pad. The invention is particularly suitable for cooperating with any type of actuator. This type of device can be used in piston brake calipers.

State of the art

In a vehicle, in particular a road vehicle, the parking brake and / or emergency brake function consists in applying and maintaining a tightening of brake pads linked to a part secured to the chassis, on a part movable in rotation which is linked to one or more several wheels, typically a disc or a drum.

In brake assemblies using one or more electric actuators, it is known to use a screw-nut system to exert a linear support on the pad, often by means of a piston. Such a configuration is for example described in the document FR2999257. This type of configuration exists for electrical operation alone, or in combination with a hydraulic actuation of this piston or another.

In FIGURE 1 is illustrated, in the case of a disc brake with hydraulic service braking and electric parking brake, a disc brake caliper 1 currently known, comprising a housing 11 enclosing a disc 19 and its friction track between friction linings or pads 17, 18. In this sliding caliper type assembly, these elements are clamped against the fingers 101 of the caliper by a piston 13 moving in translation in an actuating direction A2. In service brake mode, this piston is moved in its housing 150 by a hydraulic pressure brought by a fluid inlet 15. In parking brake mode, the piston is moved by a nut 122 fixed in rotation cooperating with a threaded rod 121 driven in rotation along the axis A2, forming a linear actuator. The screw 121 is driven by an input shaft 129 driven by a geared motor (not shown).

When the threaded rod is rotated by the gearmotor, the nut must remain stationary in rotation in the brake piston to move in translation, and thus act on at least one brake shoe by means of the piston. In this type of device, the support head of the nut is formed by four peripheral surfaces which, in a plane transverse to the nut, form a square profile. The nut is screwed onto the screw and the screw-nut system is inserted into a housing of the piston so that the head of the nut cooperates by complementary shape with the housing of the piston, of complementary square shape. The nut is in one piece.

In this type of device, the anti-rotation shape of the head of the nut is typically produced by forging, to produce this irregular shape and guarantee it sufficient strength. The internal thread is typically produced by machining.

Depending on the braking performance required, for example for vehicles of different weights, it is conventional to use different sizes of actuators and different sizes of pistons, by manufacturing the nut as a function of the width of the piston housing. This results in a significant manufacturing cost.

The object of the present invention is to overcome all or part of the drawbacks of the state of the art, and in particular to reduce the weight and the manufacturing cost of the brake mechanism for one or more models, while allowing maintenance or an increase in strength performance and better flexibility in industrialization and manufacturing.

Statement of the invention

According to a first aspect of the invention, at least one of the objectives is achieved with a nut device, for a screw-nut mechanism intended to apply an axial clamping force on a brake piston from a drive. rotary, within a motorized actuator.

According to the invention, the nut device comprises a metal wire. The metal wire comprises a portion wound so that it forms a helical winding capable of being screwed around a threaded actuating shaft. The helical winding of the wire includes:

- longitudinally a first end, called "rear end" facing said rotary drive, and a second end, called "front end" facing a rear support face of the piston, and

- radially an internal part and an external part.

The helical winding of the wire is inserted or arranged to be inserted, for example by screwing:

on the one hand, in contact with its internal part, in a helical groove carried by the external surface of the threaded actuating shaft, said helical winding thus forming a screw-nut mechanism with said threaded actuating shaft, and

- on the other hand, in contact with its external part, in a helical groove carried by the inner surface of a bore formed in an actuating sleeve.

The helical winding is typically inserted by screwing around the threaded actuating shaft and inside the actuating sleeve. Each helical groove is arranged and configured to conform in a complementary manner to the helical winding.

The helical winding thus fulfills a nut function vis-à-vis the threaded actuation shaft, and a screw function with respect to the actuation sleeve.

According to the invention, the metal wire comprises at least one portion called said rotation stop of said wire. The rotation stop portion protrudes radially around said helical winding so as to cooperate by engagement of shapes with at least one stationary part in rotation relative to said actuating sleeve to stop the rotation of said helical winding. The rotation stop portion is arranged and configured so as to perform the anti-rotation function in a manner equivalent to the nut head existing in the prior art. The metal wire is shaped, for example folded or curved, for example to produce a general geometric shape arranged and configured to act in the same way as a nut head having a polygonal geometric profile.

The metal wire is easily shaped so that it is possible to produce, at low cost, rotating stop portions of various shapes and sizes, to adapt to each brake piston housing. The actuation sleeve model can then be the same for several different sizes of actuators or pistons, each time choosing a helical winding whose rotation stop portion is adapted to the brake piston; which offers better flexibility and modularity of assembly. This also makes it possible to reduce the number of different references for the actuating sleeve, within a range of several dimensions of brake actuator and / or brake piston.

The use of metal wire makes it possible to produce specific forms of threads as required, to be more flexible to design and therefore to be able to reduce the manufacturing cost. The metal wire can for example be easily shaped so that its section has a round, square or triangular shape.

The nuts of the prior art need to be forged to make the support head, then machined to make the tapping. In addition, they often have to undergo a plastic deformation operation to finalize and / or reinforce the profile of the tapping by work hardening. Such operations are complex and costly, in particular inside a bore.

On the contrary, the metallic wire is a semi-finished product easily available and at low cost, even for high performance. The use of metal wire also makes it possible, if necessary, to carry out additional treatments (for example thermal, chemical, mechanical) which are easier to carry out than on the internal surfaces of the nut of the prior art.

The use of metal wire, to achieve the anti-rotation function of the nut, rather than a solid piece as in the prior art, makes it possible to reduce the diameter and therefore the weight of the actuating sleeve, and so the whole nut.

Due to its intrinsic properties, the metal wire also makes it possible to absorb or absorb shocks against stops.

Preferably, the metal wire comprises a portion, called the end stop, made by a portion of metal wire which projects from the first end of the helical winding. The end-of-travel stop portion makes it possible to absorb the shocks between the actuating sleeve and the threaded actuating shaft during a rotary drive in the direction of releasing the brake or unscrewing the threaded shaft d actuation. The abutment portion cooperates by engagement of shapes with an angular abutment element arranged on the threaded actuating shaft, to stop in rotation said helical winding at the end of the stroke, during a rotation drive in the direction of loosening of the brake. The limit stop portion is for example the distal end of the wire, or may be an attached part.

The limit stop portion is, according to one embodiment, an extension of the metal wire which extends from the first end of the helical winding. This extension is then in one piece with the wire of the helical winding, and is for example produced by bending the wire. The abutment portion can also be added, for example fixed by welding.

According to another embodiment, the limit stop portion is produced by a part of the metal wire extending in one piece from the first end of the helical winding and deviates radially and / or possibly longitudinally from said helical winding to form an elbow which cooperates by engagement of shapes with an angular stop element arranged on the threaded actuating shaft.

Preferably, the angular abutment element projects radially from the threaded actuating shaft.

The angular stop element is located on the threaded actuation shaft so that, when it is reached by the end of travel stop portion of the winding, the actuation sleeve has ceased to apply a force axial on the rear face of the piston. This end of travel stop function makes it possible to prevent the wound portion from coming out of the helical groove of the threaded actuating shaft. Because the end stop portion is integral with the wire winding, it also has a much higher elasticity than if it were part of a one-piece nut. When it meets the angular stop, the shock is absorbed by this elasticity, and the stop at the end of the race is thus much less brutal, which greatly improves the reliability of the mechanism.

According to one embodiment, which may be compatible with the preceding characteristics, the rotation-stopping portion is produced by a portion of metal wire which extends in one piece from the second end of the helical winding. This characteristic makes it easier to assemble with respect to the actuating sleeve by introducing the wound portion on the side of the front face of said sleeve.

According to another embodiment, the rotational stop portion is produced by a metal wire extending from the first end of the helical winding and departs at least radially from the helical winding. The metal wire extends in the direction of the second end until it forms the rotation stop portion in at least one plane transverse to the axis of the helical winding. For example, the metal wire extends in the direction of the second end along the longitudinal outer surface of the actuating sleeve up to at least one plane transverse to the axis of the helical winding.

In the various embodiments, the at least one portion of the metal wire in rotation is preferably stopped by at least one loop formed in a plane transverse to the axis of the helical winding by a portion of the metal wire which is folded or curved outward to deviate from the winding diameter. The folds of the wire make it possible to produce the rotation stop portion with shapes specifically determined to cooperate with the specific shape of the interior housing of the brake piston for which the actuator is intended.

Preferably, the portion of rotation stop of the wire comprises several lobes each cooperating by angular abutment with a shape accident inside the stationary piece in rotation to achieve a stop in rotation. Each lobe is produced by at least a part of the metal wire which successively departs radially from the helical winding and then returns towards the diameter of said winding. Preferably, the lobes are arranged along the outer surface of the actuating sleeve. The lobes move apart radially from the outer surface of the actuating sleeve, and return to the outer surface of the actuating sleeve so that the portions of metal wire between the lobes each form a hollow which is supported on the outer surface of said muff. This characteristic makes it possible to stiffen the nut device during rotary drive.

The rotation stop portion is for example made by bending the wire from the winding, but can also be added for example by welding.

Preferably, the metal wire is of circular section. This characteristic has the advantage of proposing a wire which is easily inserted into the helical grooves. According to other embodiments, the metal wire can be of square or triangular section.

Preferably, the metal wire is made of spring steel. This allows for example to promote shock absorption and / or to facilitate the assembly of the metal wire on the actuating sleeve.

Optionally, the metal wire is treated thermally and / or mechanically in order to improve its surface condition, its hardness and its resistance. This characteristic makes it possible for example to improve the efficiency of the screw-nut mechanism. In addition, it is significantly easier to implement on the outer surfaces of a wire than on the internal thread of a thread.

According to a second aspect of the invention which is in accordance with the first aspect, the nut device comprises an actuating sleeve which receives the helical winding. This actuating sleeve longitudinally comprises a first end, called the “rear end”, facing the rotary drive, and a second end, called the “front end”, the cross section of which corresponds to the front face of the support or face d '' axial support.

The actuating sleeve is provided with a longitudinal bore which is coaxial with the actuating shaft. This bore carries a helical groove arranged to receive the helical winding. Said actuating sleeve has on the side of the second end an axial bearing face arranged to apply an axial thrust force on the rear face of a brake piston. Said actuating sleeve thus forms a support sleeve.

Said support sleeve forms, with the metal wire, a nut which is displaced in translation when the threaded actuating shaft is rotated on the side of the first end while the helical winding and the sleeve are stopped in rotation by the portion of rotation stop of said helical winding. This rotation stop is achieved by cooperation of shapes of the rotation stop portion with a housing inside said brake piston, or with an element fixed to the housing and including or not including said brake piston.

This actuating sleeve thus makes it possible to transmit the axial thrust force:

- while maintaining radially, thanks to its bore, the helical winding along the external part of the shaft, and

- by keeping the stop portion in rotation radially so that it remains engaged in the piston housing, holding effected by the external surface of the actuating sleeve.

Preferably, the axial bearing face of said sleeve comprises at least one groove which diverges radially on the outer surface of said sleeve. The groove diverges radially, for example in a sagittal plane around the axis. Said groove is arranged and configured to receive a section of the metallic wire of the winding, so as to stop the rotation of the support sleeve relative to the helical winding. The section of the wire is a connecting portion of the wire for example, a part of the stop portion in rotation or a part of the end stop portion.

Preferably, the support sleeve comprises on the side of its second end a flange so that the support face corresponds to the cross section of the flange.

Optionally, the shape of the bearing face is frustoconical, or has a chamfer, in order to bear on the rear face of the brake piston.

According to one embodiment of the at least one groove, this (s) is (are) made (s) on the bearing face of the sleeve.

According to another embodiment, a groove is arranged on the outer surface of the sleeve, at its first end.

The positions of the grooves have the advantage of being made near an existing passage of the metal wire.

According to a third aspect of the invention, which can be in accordance with one or both of the two preceding aspects, the nut device comprises an actuating sleeve which receives the helical winding in its bore and which is immobilized in rotation, said sleeve having on the side of the second end an axial bearing face arranged to apply an axial thrust force on the rear face of a brake piston, said helical winding receiving on the surface of its internal part a shaft of actuation which is rotated on the side of the first end, thereby forming a rotating shaft, said actuating sleeve thus forming a nut which is moved in translation when the actuating shaft is rotated.

According to a fourth aspect of the invention, which can be in accordance with the first aspect, the nut device comprises an actuating sleeve which receives the helical winding in its bore and which is rotated on the side of the first end, thus forming a rotating nut, said helical winding receiving on its internal surface an actuating shaft immobilized in rotation and having, on the side of the second end, an axial bearing face arranged to apply an axial thrust force on the rear face a brake piston, said actuating shaft thus forming a screw which is moved in translation when the actuating sleeve is rotated.

The invention also relates to a vehicle brake comprising at least one nut device according to one or more of the preceding aspects, or including at least one actuator comprising a nut device according to one or more of the preceding aspects .

According to another aspect of the invention, in accordance with one or more of the preceding aspects, there is provided a method for assembling a brake or a brake actuator comprising a nut device according to one or many of the previous aspects. The assembly process is characterized in that it comprises the following stages:

- supply of a support sleeve, having a determined internal geometry, for example in the dimensions of the helical groove;

supply of a brake piston comprising a support housing arranged to receive an axial support (to produce a clamping force) on the part of said support sleeve and having an anti-rotation shape of a determined geometry, by example in shape and dimensions - this piston is for example selected from a plurality of brake pistons having different internal geometries of housing - and typically which also have different external diameters;

- Among a plurality of helical windings having different geometries, selection of a helical winding having a geometry compatible with the internal geometry of said sleeve, with the external geometry of said actuation shaft, and with the internal geometry of said piston; and

- Assembling said support sleeve with said helical winding to form a nut device, according to one or more of the preceding aspects, capable of cooperating with the interior housing of said brake piston to stop rotation of said nut device.

Description of the figures and embodiments

Other characteristics and advantages of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, with regard to the appended figures in which:

- FIGURE 1 is a view in longitudinal section along the axis of the piston, which illustrates a hydraulic disc brake caliper carrying a motorized parking brake actuator comprising a screw-nut mechanism, according to the prior art;

- FIGURES 2a and 2b are perspective views showing a nut device, according to one embodiment with a stop portion from the first end, in a piston seen in a longitudinal section, FIGURE 2b having the same actuating sleeve but a rotation stop portion and a piston of larger dimensions than in FIGURE 2a;

- FIGURES 3a and 3b are perspective views of a metal wire comprising a rotation stopping portion according to another embodiment with a stopping portion coming from the second end, and an actuating sleeve which can be in accordance with FIGURES 2a and 2b:

FIGURE 3a exploded showing the actuation sleeve seen in perspective, the body of which is seen in a longitudinal section, and the metal wire,

- FIGURE 3b showing the actuating sleeve, seen in perspective and in longitudinal section, and the metal wire assembled together and mounted on a threaded actuating shaft;

- FIGURES 4a and 4b are perspective views showing in the assembled position the wire according to FIGURES 3a and 3b and the head of the actuating sleeve:

- FIGURE 4a in a longitudinal section,

- FIGURE 4b showing the stop portion in rotation relative to the entire head of the support sleeve;

- FIGURES 5a and 5b are perspective views showing the cooperation between the metal wire, comprising a stop portion in rotation according to an embodiment in accordance with FIGURES 2a and 2b, and the rear end of the body of the sleeve actuation, in an embodiment with a stop portion coming from the first end:

FIGURE 5a showing said stop portion in partial view, assembled with an actuating sleeve in view in a longitudinal section,

- FIGURE 5b showing a partial zoom of the rear end of an actuating sleeve which has a groove in which a section of the rotating stop portion is inserted;

- FIGURE 6 is a top view of a nut device in the end-of-travel stop position on a threaded actuating shaft, a section of the metal wire coming to bear against an angular stop element projecting from said shaft .

Description of the embodiments

The embodiments which will be described are in no way limiting; it will be possible in particular to implement variants of the invention comprising only a selection of characteristics described subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from in the prior art. This selection comprises at least one characteristic, preferably functional, without structural details, or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art.

In particular, all the variants and all the embodiments described can be combined with one another if there is nothing technically opposed to this combination.

FIGURE 2a and FIGURE 2b illustrate a brake piston 50 for the brake caliper, the brake piston being arranged and configured to translate by a screw-nut mechanism, from left to right, or vice versa, from a drive rotary, not shown. The screw-nut mechanism is disposed inside a support housing 52 formed in the rear face of the brake piston 50. Said brake piston is designed to exert an axial force on a shoe which is intended to tighten a brake disc (not shown), for example similar to that of FIGURE 1. The brake piston is immobilized in rotation relative to the brake housing surrounding said piston.

The rotary drive is designed to rotate the screw of the screw-nut mechanism, while the nut of the screw-nut mechanism is immobilized in rotation in the support housing 52 of the piston. Said nut is arranged and configured to move in translation when the screw is rotated; and to apply an axial thrust force on a rear support face of the piston in one direction, or retract and let the piston return in the other direction.

The screw-nut mechanism comprises a threaded actuating shaft 40 and a nut device 10, said device being arranged around said shaft. The nut device 10 comprises a metal wire 20 and an actuating sleeve 30. The metal wire is arranged to cooperate by complementary contact with at least part of the threaded actuating shaft. The actuating sleeve is arranged to cooperate by complementary contact with the metal wire. When the threaded actuating shaft is rotated in order to apply the brake disc, the actuating sleeve 30 translates via the metal wire 20 towards a rear bearing face 51 of the brake piston 50. Once the sleeve in contact with the rear support face 51 of the brake piston 50, the sleeve exerts an axial thrust force against said face.

The metal wire 20 comprises a wound portion 21 so that it forms a helical winding capable of being screwed around a threaded actuating shaft 40 of axis Al. The helical winding 21 comprises several turns, for example in proportion to the number of threads of the screw and preferably in sufficient number to preferably cover a length of at least once the diameter of the screw and / or less than twice this diameter.

For example, the helical winding comprises from 5 to 10 turns. The turns have a constant diameter along the longitudinal direction of the helical winding. Referring to FIGURES 2a, 2b, 3a and 3b, the helical winding 21 includes longitudinally a first end, called "rear end" 21b facing the rotary drive, not shown, and a second end, called "front end" 21f, facing the rear support face 51 of the piston 50. The helical winding 21 of the wire has a generally substantially cylindrical shape so that it includes radially an internal part and an external part. The term “internal part of the helical winding of the wire” means the surface of the wire oriented radially towards the axis of the winding A1. With reference to FIGURES 2a, 2b and 3b, the internal part of the helical winding is in contact complementary with a helical groove 41 carried by the outer surface of the threaded actuating shaft. The helical winding 21 forms a nut. The threaded actuation shaft 40 forms a screw so that it forms, with the helical winding, a screw-nut mechanism. By external part of the helical winding 21 is meant the surface of the wire oriented radially outward of the helical winding. With reference to FIGURES 2a, 2b and 3b, the external part of the helical winding is in complementary contact with a helical groove 31 carried by the internal surface of a bore formed in an actuating sleeve 30. The helical winding 21 cooperates simultaneously with the helical groove 41 of the threaded actuating shaft 40 and the helical groove 31 of the actuating sleeve 30. The actuating sleeve is described below.

With reference to FIGURES 2a, 2b, 3a and 3b, the metal wire 20 comprises a so-called rotation-stopping portion 25 of said wire. The rotation stop portion protrudes radially around said helical winding 21 so as to cooperate by engagement of shapes with the housing 52 of the brake piston to stop the rotation of said helical winding relative to said piston (see FIGURES 2a and 2b). With reference to FIGURES 2a, 2b, 3a and 3b, the rotation stop portion 25 forms a pattern which is arranged in a plane transverse to the axis of the helical winding. With reference to FIGURES 3a or 3b and by way of example, the rotation stop portion is situated in a transverse plane which is here substantially coincident with or offset, for example by a few millimeters, for example 5 to 20 millimeters, relative to a transverse plane comprising the front end 21f. The rotation stop portion 25 protrudes radially around the body 32 of the actuating sleeve 30. The rotation stop portion has, relative to the axis A1, a non-cylindrical circumferential shape.

Preferably, the rotation stop portion is produced by one or more loops or turns formed in a plane transverse to the axis of the helical winding. The metal wire is folded outward to deviate from the diameter of the winding 21 to produce the rotation stop portion 25. According to a preferred embodiment, the rotation stop portion 25 comprises lobes 25L and hollows 25C. The stop portion in rotation of the wire comprises several folds so as to form a succession of stop shapes, here lobes 25L and hollows 25C along said loop. Each lobe 25L cooperates with a form accident inside the housing 52 of the piston 50, by pressing the wire 20 in at least one circumferential direction around this axis thus forming an angular stop. This cooperation thus achieves a rotation stop of the winding 21 relative to said piston (see FIGURES 2a and 2b), and therefore relative to the brake housing, here the caliper. Each lobe 25L is produced by at least a portion of the metal wire which successively departs radially from the helical winding and then returns towards the diameter of said winding. The section of metal wire between two successive lobes forms a hollow 25C. For example, with reference to FIGURE 3a, the rotation stop portion comprises four lobes 25L and four recesses 25C. The shape of the lobes is arranged and configured to conform to the adjacent faces of the piston housing 50. For example, with reference to FIGURES 3a and 3b, the metal wire of the stop portion is bent so that said portion has a shape generally substantially square, the lobes 25L being folded to conform to a corner of a substantially square housing. According to a preferred embodiment, each recess 25C of the rotation-stopping portion is provided to follow a portion of the periphery of the cylindrical body of the sleeve 30. Preferably, each recess 25C is arranged and configured to bear radially on the peripheral surface of the body 32 of the sleeve, and / or be held axially in a circumferential groove carried by this peripheral surface. This characteristic makes it possible, for example, to maintain the stop form axially and to prevent the rotation stop portion from twisting during the rotation drive of the threaded actuating shaft.

According to a first embodiment of the rotating stop portion represented by FIGURES 3a and 3b, the metal wire of said stop portion is extended in one piece from the second end 21f of the wound portion 21 to form a connecting portion 24f between the wound portion 21 and the rotation-stopping portion 25. At the start of the connecting portion, the wire 20 comes out of the helical groove 41 of the threaded actuating shaft and extends longitudinally towards the rear bearing face 51 of the piston, so that the connecting portion 24f runs along the surface of the bore of the sleeve in a wider part 37 which is not tapped. The metal wire then spreads radially along the front face of support of the sleeve in a radial groove 34, then it follows this groove 34 while returning towards the first end along the external surface of the actuating sleeve 30. In this example, we can consider that the connecting portion 24f ends once it has traversed the groove 34. The wire then goes around the sleeve in a plane transverse to the axis of the winding, along a path which achieves the stop form of the rotating stop portion. In the present example, this transverse plane comprises the second end 21f of the wire of the wound portion.

According to a second embodiment of the rotation stop portion represented by FIGURES 2a, 2b, the metal wire of said portion extends in one piece from the first end 21b of the wound portion 21. In the present example , the wire 20 comes out of the helical groove 41 of the threaded actuating shaft and extends longitudinally towards a flange 42 of the threaded actuating shaft, then diverges radially as far as the outer surface of the body 32 of the actuating sleeve 30, see FIGURES 2a, 2b. Referring to FIGURES 2a and 2b, the wire then returns to the second end 21f of the wire of the wound portion, then circles the sleeve in a plane transverse to the axis of the winding, along a path which achieves the shape stopping the rotation stopping portion, here in a transverse plane which comprises said second end of the winding. In the present example, the portion of metal wire 20 between the first end 21b and the rotation-stopping portion 25 provides a connecting portion 24b forming an elbow and a portion of straight wire 25T which runs longitudinally along the outer surface of the sleeve.

In the present examples, the wire connection portion is integral with the wire of the winding, and is obtained by bending with respect to the wound portion 21. Alternatively, all or part of the elements external to the helical part of the winding are also provided to be produced in the form of an attached part, for example by welding after assembly with the actuating sleeve.

It will be noted that these embodiments can also be combined with one another, for example by producing a rotation stop portion which is integral with both the first end and the second end, for example by at least one welded connection.

The actuating sleeve 30 has the shape of a cylindrical tube 32, the bore of which is tapped so as to comprise as many steps, or for example more or less two steps, as there are turns of the helical winding. This characteristic makes it possible to transmit the axial thrust force by distributing it over several threads of the sleeve and of the shaft. With reference to FIGURES 3a, 3b, 4a, 4b and 6, the actuating sleeve comprises a head 33 having an axial bearing face 35 arranged and configured to bear against a rear face of the brake piston. Preferably, the head 33 of the sleeve has the shape of a collar disposed at the end of the sleeve opposite the rear bearing face 51 of the piston. With reference to FIGURES 3a, 3b, 4a, 4b and 6, the bearing face 35 of the sleeve has the shape of a chamfer, preferably of revolution around the axis and for example conical or ovoid or spherical. With reference to FIGURES 5a and 6, the head 33 includes a rear face 36, opposite the front support face 35. With reference to FIGURE 4b and 6, the rotation stop portion 25 extends and can take support, at the level of the recesses 25C, against the rear face 36 of the head 33.

Preferably, the head 33 includes head grooves 34f. Said grooves 34f extend radially on the external surface of the axial bearing face 35 and extend longitudinally on the peripheral surface of the head 33 to the rear face 36. With reference to FIGURES 3b, 4a and 4b, each groove 34f is arranged and configured to receive in a complementary manner a longitudinal section of metal wire so as to stop the rotation of the actuating sleeve relative to the helical winding. Each groove 34f is here provided to receive a longitudinal part of the connecting portion 24f. This embodiment is particularly suitable for a rotation stop portion formed according to the first embodiment.

According to one embodiment, and with reference to FIGURES 5a and 5b, the rear end of the body 32 of the sleeve comprises a rear groove 34b extending longitudinally on the exterior surface of said body 32. The groove 34b is here arranged and configured to receive a section of metal wire of the rotation stopping portion, according to the second embodiment, so as to stop the rotation of the actuating sleeve relative to the helical winding. Preferably, the groove 34b is embedded in the outer surface of the body 32 of the actuating sleeve in order to receive the connecting portion 24b of the wire.

Preferably, each actuating sleeve 30 comprises the grooves 34f and the groove 34b. The same type of sleeve can be used for all types of screw-nut mechanism or all types of brake piston. In addition, this reduces the weight of the nut device.

With reference to FIGURE 6, the metal wire 20 comprises a portion, called the end stop 27, produced by a portion of metal wire which extends from the first end of the helical winding. This embodiment of the stop portion 27 is shown here with a rotation stop portion according to the second embodiment, but can also be achieved with a rotation stop portion produced according to the first embodiment. The abutment portion 27 of the wire 20 cooperates by pressing on an angular abutment element 43 arranged on the threaded actuating shaft 40, to stop in rotation said helical winding during a drive in rotation in the direction of release of the brake . The angular stop element 43 comprises a shoulder which protrudes radially from the helical groove 41 and forms a stop for the rotation of the winding relative to the actuation shaft. Therefore, it also forms an end-of-travel stop in translation for the nut device formed by the metal wire 20 and the actuating sleeve 30, in the direction of the return towards the rear, that is to say of the loosening. Preferably, the abutment portion 27 is produced by a metal wire extending longitudinally in one piece from the first end 21b of the helical winding to form an elbow which cooperates by form engagement with said abutment element 43. with reference to FIGURE 6, the angular stop element is formed on the flange 42 of the threaded actuating shaft 40 and projects axially with respect to the flange and radially with respect to the helical groove 41. With respect to a nut of the prior art, the use of the metallic wire which protrudes from the groove introduces a flexibility and an elasticity which makes it possible to absorb shocks at the end of the stroke during a rotation drive in the direction of releasing the brake .

The assembly of the screw-nut mechanism will now be described.

When assembling the screw-nut mechanism according to the first embodiment of the rotation stop portion, the metal wire 20 is introduced into the bore of the actuating sleeve 30 on the side of the axial bearing face 35. The wound portion 21 is screwed into the helical groove 31 of the sleeve like a screw. The wire 20 is screwed until the connection portion 24f fits into one of the grooves 34f of the head 33, the assembly forming the nut device. Then, the nut device is screwed around the threaded actuating shaft 40 via the wound portion 21. Optionally, the second end of the winding comprises a portion of wire, protruding longitudinally, which is folded outwards after screwing into the sleeve. This part can optionally be then fixed to the end of the wire which comes from the first end of the winding, for example by welding.

During the assembly of the screw-nut mechanism according to the second embodiment of the rotation stop portion, the metal wire 20 is screwed around the threaded actuating shaft 40. Then, the actuating sleeve 30 is screwed onto the wound portion 21 of the metal wire on the side of the second end 21f. The sleeve is screwed until the stop portion 25 rotates against the rear face 36 of the head 33 of said sleeve. Optionally, the first end of the winding comprises a portion of wire, protruding longitudinally, which is folded outwards after screwing into the sleeve, for example to form the end stop portion. This part can optionally be then fixed to the end of the wire which comes from the second end of the winding, for example by welding.

Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention.

Nomenclature 1 disc brake caliper 10 nut device 101 stirrup fingers 11 caliper housing 12 linear parking actuator 120 actuator support part 121 actuator screw 122 actuator nut 128 actuator screw support flange 129 actuator screw input shaft 13 brake piston 15 hydraulic inlet 150 piston housing - hydraulic chamber

17, 18 friction linings

19 brake disc - friction tracks 20 wire 21 wound portion / helical winding 21b first end / rear end of the rolled portion 21f second end / front end of the rolled portion 24f front link portion 24b rear link portion 25 wire stop portion 25C stop portion trough 25L stop portion lobe 25T portion of straight wire 27 end stop portion 30 actuating sleeve 31 helical groove of the actuating sleeve 32 actuator sleeve body 33 actuator sleeve head 34 groove of the actuating sleeve 34b rear groove of the actuating sleeve 34f actuator sleeve head groove 35 axial support face / front support face

rear support face non-tapped part of the actuation sleeve threaded actuation shaft helical groove of the threaded actuation shaft flange of the threaded actuation shaft angular stop element brake piston rear support face of the brake piston brake piston support housing actuation direction - axis of the brake piston and of the nut actuation direction - axis of the brake piston (prior art)

Claims (15)

1. Nut device (10), for a screw-nut mechanism intended to apply an axial clamping force on a brake piston (50) from a rotary drive, within a motorized actuator, characterized in that it comprises a metal wire (20) comprising a wound portion (21) so that it forms a helical winding capable of being screwed around a threaded actuating shaft (40), the helical winding (21) wire comprising: - longitudinally a first end (21b), called "rear end" facing said rotary drive, and a second end (21f), called "front end" facing a rear bearing face (51) of the piston, and - radially an internal part and an external part, so that the helical winding (21) of the wire is inserted or arranged to be inserted: - on the one hand, in contact with its internal part, in a helical groove (41) carried by the external surface of the threaded actuating shaft (40), said helical winding (21) thus forming a screw-nut mechanism with said threaded actuating shaft (40), and - on the other hand, in contact with its external part, in a helical groove (31) carried by the inner surface of a bore formed in an actuating sleeve (30), and in that said metal wire (20) comprises at least one portion called rotation stop (25) of said wire, which protrudes radially around said winding (21) so as to cooperate by engagement of shapes with at least one stationary part in rotation relative to said actuating sleeve for stopping the rotation of said helical winding (21). 2. Nut device (10) according to claim 1, characterized in that the metal wire (20) comprises a portion, called the end stop (27), produced by a portion of metal wire which protrudes from the first end (21b) of the helical winding (21), and in that said abutment portion (27) cooperates by engagement of shapes with an angular abutment element (43) arranged on the threaded actuation shaft (40 ), to stop in rotation said helical winding (21) at the end of the stroke, during a rotary drive in the direction of release of the brake. 3. Nut device (10) according to one of claims 1 to 2, characterized in that the end-of-travel stop portion (27) is produced by a part of the metal wire (20) extending from in one piece from the first end (21b) of the helical winding (21) and departs radially and / or longitudinally from said helical winding to form an elbow which cooperates by engagement of shapes with an angular stop element (43) arranged on the threaded actuating shaft (40), said angular stop element (43) projecting radially from the threaded actuating shaft. 4. nut device (10) according to one of claims 1 to 3, characterized in that the rotation-stopping portion (25) is produced by a portion of metal wire which extends in one piece from the second end (21f) of the helical winding (21). 5. nut device (10) according to one of claims 1 to 4, characterized in that the rotation-stopping portion (25) is produced by a metal wire (20) which extends from the first end ( 21b) of the helical winding (21) and deviates (at least) radially from the helical winding, then extends in the direction of the second end (21f), until forming the rotation stop portion (25) in at least one plane transverse to the axis of the helical winding. 6. nut device (10) according to any one of the preceding claims, characterized in that the at least one portion of rotation stop (25) of the metal wire is produced by at least one loop formed in a plane transverse to the axis of the helical winding by a portion of the metal wire which is folded outwards to deviate from the diameter of the winding. 7. nut device (10) according to the preceding claim, characterized in that the rotation-stopping portion (25) of the wire comprises several lobes (25L) each cooperating with an accident of shape inside the part stationary in rotation to achieve a stop in rotation, each lobe (25L) being produced by at least part of the metal wire which successively departs radially from the helical winding (21) then returns towards the diameter of said winding. 8. Nut device (10) according to any one of the preceding claims, characterized in that the metal wire (20) is of circular section. 9. Nut device (10) according to any one of the preceding claims, characterized in that the metal wire (20) is made of spring steel. 10. Nut device (10) according to any one of the preceding claims, characterized in that it comprises an actuating sleeve (30) provided with a longitudinal bore carrying a helical groove (31) arranged to receive the helical winding (20), said actuating sleeve having on the side of the second end (21f) an axial bearing face (35) arranged to apply an axial thrust force on the rear face (51) of a piston brake (50), said actuating sleeve thus forming a support sleeve, said support sleeve thus forming a nut which is moved in translation when the threaded actuation shaft (40) is rotated from the side of the first end (21b) while the helical winding and the sleeve are stopped in rotation by the rotation-stopping portion of said helical winding. 11. nut device (10) according to the preceding claim, characterized in that the bearing face (35) of the bearing sleeve (30) comprises at least one groove (34) which diverges radially on the outer surface of said sleeve, said groove being arranged and configured to receive a section of the metal wire of the winding, so as to stop the rotation of the support sleeve relative to the helical winding (21). 12. nut device (10) according to any one of the preceding claims, characterized in that it comprises an actuating sleeve which receives the helical winding in its bore and which is immobilized in rotation, said sleeve having side of the second end an axial bearing face arranged to apply an axial thrust force on the rear face of a brake piston, said helical winding receiving on its internal part an actuating shaft which is driven in rotation from the side from the first end, thus forming a rotating shaft, said actuating sleeve thus forming a nut which is moved in translation when the actuating shaft is driven in rotation. 13. Nut device (10) according to any one of claims 1 to 11, characterized in that it comprises an actuating sleeve which receives the helical winding in its bore and which is rotated on the side of the first end, thus forming a rotating nut, said helical winding receiving on its internal radial surface an actuation shaft immobilized in rotation and having, on the side of the second end, an axial bearing face arranged to apply an axial force of thrust on the rear face of a brake piston, said actuating shaft thus forming a screw which is moved in translation when the actuating sleeve is driven in rotation. 14. Vehicle brake characterized in that it comprises at least one nut device (10) according to any one of the preceding claims, or at least one actuator comprising a nut device (10) according to any one of the preceding claims. 15. A method of assembling a brake or a brake actuator comprising a nut device (10) according to any one of claims 1 to 12, characterized in that it comprises the following steps: - Supply of a support sleeve (30), having a determined internal geometry; - Supply of a brake piston comprising a support housing (52) arranged to receive a clamping force from said support sleeve and having an anti-rotation shape of a determined geometry; - from a plurality of helical windings having different geometries, selection of a helical winding (21) having a geometry compatible with the internal geometry of said sleeve, with the external geometry of said actuation shaft, and with the internal geometry of said piston ; and - Assembly of said support sleeve with said helical winding to form a nut device (10) according to any one of claims 1 to 12 capable of cooperating with the internal housing (52) of said brake piston to stop said rotation nut device.