Ball screw mechanism nut, and associated ball screw mechanism

Abstract

A nut (12) of a ball screw mechanism (1) has a nut body (20) with an outer annular face (24) on which is located a recirculation channel (38) having axial symmetry with respect to an axis of symmetry (108').The recirculation channel (38) is open on the outer annular face (24) and has a channel bottom wall (39) which has a constant radius of curvature and a center of curvature positioned on a central axis (107) of the recirculation channel (38) and two sides (39') continuous with the channel bottom wall (39) and which are symmetrical to each other on either side of a median axis (110) passing through the center of curvature, the median axis (110) making, with a radial axis (111) passing through the center of curvature, a recirculation angle (A3) which varies according to an axial abscissa of the cutting plane, measured along the central axis (107) of the recirculation channel (38), according to a continuously increasing or continuously decreasing function. (Short Figure: 7).

Description

Title of the invention: Ball screw mechanism nut, and associated ball screw mechanism. TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the field of ball screws, in particular applied to actuators, in particular to piston actuators, in particular for the transport industry, in particular automotive or aeronautical, and more particularly, although not exclusively, intended for driving brake calipers in braking mechanisms. PREVIOUS STATE OF THE ART

[0002] Document FR2101446A5 presents a ball screw mechanism nut with external recirculation, i.e., in a recirculation channel located outside a raceway of the nut, and more particularly within the nut body. The disclosed recirculation does not require an added recirculation component. Such recirculation is made possible by machining a guide channel between the recirculation channel and an external helical raceway formed on an inner face of the nut. This machining is performed in the thickness of the nut by means of a groove cut into a transverse end surface of the nut.

[0003] Such a nut has the advantage of offering ball recirculation without a "recirculator", this term designating added parts intended to guide the balls by deflecting them between the rolling path and the recirculation channel.

[0004] However, manufacturing such a nut requires machining a recirculation channel using a suitable tool. Since the recirculation channel is closed, the only possible machining method appears to be by inserting a milling cutter into the nut's bearing race and then guiding the cutter to the machining location of the recirculation channel via the open groove. Machining such a nut is therefore technically complex and appears to require excessively long manufacturing times. Furthermore, while the groove as described allows for machining the guide channels and the recirculation channel, as well as retaining the balls in the guide channel, it does not allow for retaining the lubricant of the ball screw mechanism, such as grease. It is therefore necessary to add a separate sealing element, increasing the axial dimensions. Description of the invention

[0005] The invention aims to remedy the drawbacks of the prior art and to propose a nut exhibiting recirculation without recirculators, and whose machining is greatly simplified while improving its efficiency.

[0006] To this end, according to a first aspect of the invention, a ball screw mechanism nut defining a reference axis is proposed, comprising a nut body, the nut body having an outer annular face facing away from the reference axis, an inner annular face facing towards the reference axis, on which is formed a nut thread delimiting an outer helical raceway for balls of the ball screw mechanism, a recirculation channel located radially outside the outer raceway, and two guide channels, each configured to guide the balls between an associated end of the outer helical raceway of the nut thread and an associated end of the recirculation channel, the raceway having axial symmetry with respect to an axis of symmetry perpendicular to the reference axis, the recirculation channel having axial symmetry with respect to the axis of symmetry,the two guide channels being symmetrical to each other with respect to the axis of symmetry, remarkable in that the recirculation channel is open on the outer annular face and presents • a channel bottom wall which, in any plane of section perpendicular to the reference axis, has a constant radius of curvature Rcc and a center of curvature positioned on a central axis of the recirculation channel, parallel to the reference axis and , • two sides in continuity with the bottom wall of the channel and which, in any plane of section perpendicular to the reference axis, are symmetrical to each other on either side of a median axis passing through the center of curvature, the median axis making, with a radial axis passing through the center of curvature, a recirculation angle which varies according to an axial abscissa of the plane of section, measured along the central axis of the recirculation channel, according to a continuously increasing or continuously decreasing function, preferably linear, preferably with constant derivative, preferably passing through a zero angle value in a plane containing the axis of symmetry.

[0007] The recirculation channel performs a twist on itself, allowing the sides to join the guide channels as tangentially as possible, so that the circulation of balls between said recirculation channel and the guide channels takes place without friction or blockages.

[0008] According to one embodiment, in any cutting plane perpendicular to the reference axis, the two flanks are formed by two straight line segments, preferably parallel to each other and to the median axis. The recirculation channel can then be obtained by machining from the outer annular face of the nut, by milling by For example, this type of machining is relatively simple to perform and is known to those skilled in the art.

[0009] The external helical raceway is dimensioned for balls of predetermined diameter of the ball screw mechanism, and has a characteristic rolling radius of curvature Rc r measured in any cutting plane perpendicular to the nut thread, which is greater than half the predetermined diameter of the balls.

[0010] Naturally, the radius of curvature Rcc of the channel bottom wall is greater than the radius of the balls, and preferably less than 1.1 times the radius of the balls. This dimensioning prevents excessive friction between the balls, which, in the recirculation channel, do not roll but are pushed by the balls following them. Furthermore, this dimensioning prevents the balls from staggering, pushing against each other in the recirculation channel and consequently becoming stuck. The radius of curvature Rcc of the channel bottom wall is preferably less than the characteristic rolling radius of curvature Rcr of the raceway, and the ratio is greater than 1 and less than 1.1, preferably less than 1.08.

[0011] Preferably, in any cutting plane perpendicular to the reference axis, the bottom wall of the channel forms a semicircle.

[0012] The guide channel preferably allows for the guidance of the balls by direct contact with the balls.

[0013] According to one embodiment, each of the two guide channels is constituted by, or at the very least comprises, a uniaxial bore oriented along a bore axis, the bore axis having a projection onto an end cutting plane intersecting the associated end of the recirculation channel, which is parallel, to within 5°, to the median axis located in the end cutting plane. Thus, the bore allows the lateral walls of the guide channel to correspond to the flanks at the end of the recirculation channel so that the transfer of the balls between the guide channel and the recirculation channel occurs smoothly.

[0014] According to one embodiment, the drilling is a cylindrical hole having an internal diameter such that the ratio ~~ is greater than 1 and less than 1.2, preferably less than 1.09. The drilling is a simple machining operation to perform, allowing the manufacturing time of the nut and the associated costs to be reduced, while maintaining the guiding function of the guide channels.

[0015] According to one embodiment, viewed in projection onto a plane perpendicular to the reference axis, the drilling axis forms an internal angle greater than 25°, preferably greater than 33°, and less than 45°, preferably less than 37°, with a tangent to a bottom cylinder of the path on which is located a helical bottom of the path of The external helical bearing passes through an internal intersection point between the drill axis and the bottom cylinder of the raceway. The chosen angle allows the drill to be relatively in line with the raceway at its end. In other words, the change of direction for the balls leaving the raceway to enter the drill, or leaving the drill to roll along the raceway, is not too abrupt.

[0016] According to one embodiment, the recirculation channel has a channel bottom line located on a channel bottom cylinder centered on the reference axis and having a predetermined diameter, and the drill axis has an external intersection point with a channel center cylinder centered on the reference axis and having a diameter equal to the sum of the diameter of the channel bottom cylinder and the ball diameter. Viewed in projection onto a longitudinal plane comprising the reference axis and the external intersection point, the drill axis forms an external angle greater than 45°, preferably greater than 55°, and less than 75°, preferably less than 65°, with the channel center cylinder.The outer intersection point corresponds to the approximate positioning of a ball center at the intersection between the bore and the recirculation channel, and the range of angular values ​​defined at this location guarantees an acceptable change of direction for balls leaving the recirculation channel to enter the bore, or leaving the bore to enter the recirculation channel.

[0017] Such a drilling axis allows a smooth transfer of balls between the external helical raceway of the nut and the recirculation channel, i.e. without excessive friction against the walls of the drilling, the recirculation channel or the raceway.

[0018] According to one embodiment, the channel bottom line is straight and parallel to the reference axis. The recirculation channel then has the shortest possible track bottom, increasing the active ball ratio, that is, the ratio of the number of active balls present in the outer helical raceway of the nut to the total number of balls present in the recirculation channel and the guide channel. Thus, the efficiency of such a nut is improved.

[0019] According to one embodiment, the nut body comprises, at the end of the outer helical raceway, a concave guide wall projecting radially towards the reference axis relative to the bottom of the outer helical raceway, seamlessly joining the guide channel with a flank of the outer helical raceway, and guiding the balls between the guide channel and the outer helical raceway. The concave guide wall thus allows the balls to be guided progressively, in the manner of a scoop.

[0020] According to one embodiment, the nut includes an added deflector, a scoop for example, comprising a bearing surface intended to bear against a positioning surface in tangent and continuous contact with an annular end bearing surface of the nut, and an extension surface, intended to extend the guide wall of the nut, located in the extension of the bore opposite the external helical bearing race.

[0021] According to one embodiment, the deflector includes a positioning tab intended to bear fixedly against the inner annular surface of the nut.

[0022] According to one embodiment, the extension surface generally has a spherical cap shape.

[0023] The deflector projects radially from the nut threads forming the flanks of the nut's outer helical raceway and is designed to fit between the flanks of the screw's inner helical raceway. This deflector is intended to contact the portion of the balls that protrudes from the nut threads and improves ball guidance, extending from the guide wall. Furthermore, the spherical cap shape allows for a better match between the spherical shape of the balls, the raceway on which they are located before being guided, and the guiding properties of one end of the raceway.

[0024] The deflector can be fixed to the body of the nut by any suitable means, for example by means of a pin.

[0025] According to one embodiment, the deflector is a constituent part of an annular seal attached to the nut, the deflector being fixedly connected, via the positioning tab, to said annular seal, preferably the annular seal comprises an annular body around the reference axis of the nut intended to be aligned with a helix axis of the nut, the annular body comprising an outer annular surface bearing against the nut, preferably against the inner annular face, in a bearing direction having a radial component with respect to the reference axis.

[0026] Such a seal allows for better attachment of the deflector to the nut thanks to a press fit of the seal into the nut, the seal being dimensioned to be shrink-fitted into the nut. Furthermore, the annular seal includes a sealing lip extending radially inward from the annular body of the seal, and the sealing lip makes at least half a helix turn, preferably at least three-quarters of a helix turn. Thus, the seal improves the retention of a lubricant in the ball screw mechanism, such as grease.

[0027] According to one embodiment, the deflector positioning tab is fixedly linked to the annular body of the annular seal, the deflector being axially projecting relative to the annular body, allowing the deflector to be positioned in a position of use, more particularly in the external helical raceway, at the level of the rolling end of the raceway.

[0028] According to one embodiment, the nut includes another guide channel, configured to guide the balls between another end of the outer helical raceway of the nut thread opposite the end of the outer helical raceway of the nut thread and another recirculation end of the recirculation channel opposite the recirculation end of the recirculation channel, by direct contact with the balls, and includes another oriented bore, preferably along another bore axis which has a radial component identical to that of the bore axis, and, preferably still, an orthoradial component and an axial component, both opposite to those of the bore axis, the other bore opening onto the inner annular face at the other bearing end of the outer helical raceway and onto the outer annular face at the other recirculation end of the recirculation channel.Since the two guide channels are identical by axial symmetry, they therefore exhibit equivalent guiding properties.

[0029] According to another aspect of the invention, a nut device is notable in that it comprises a nut as described above and a sleeve, the sleeve being configured to come into contact with the outer annular face of the nut body and, where applicable, to close the open recirculation channel. The sleeve allows the bore, and where applicable the recirculation channel, to be closed, and may have properties adapted to the environment in which it will be used.

[0030] According to another aspect of the invention, a ball screw mechanism, in particular for a brake actuator, notable in that it comprises a nut or a nut device as described above, a screw and balls circulating between an inner helical raceway formed by the screw and the outer helical raceway of the nut, the nut and / or the sleeve and / or the screw preferably forming a piston configured to actuate the brake, allowing the brake actuator mechanism to benefit from all the advantages of such a nut. BRIEF DESCRIPTION OF THE FIGURES

[0031] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures.

[0032] [Fig.1] Fig.1 illustrates an exploded view of a ball screw mechanism, comprising a nut, a screw and at least one ball, and a seal comprising a deflector.

[0033] [Fig.2] The [Fig.2] illustrates the nut incorporating the seal in a cutting plane perpendicular to a reference axis.

[0034] [Fig.3] Fig.3 illustrates an isometric view of the nut.

[0035] [Fig.4] Fig.4 illustrates the drilling axes of the nut in a cutting plane perpendicular to the reference axis.

[0036] [Fig.5] Fig.5 illustrates the nut in a longitudinal section plane.

[0037] [Fig.6] Fig.6 illustrates one end of a nut bearing race integrating the joint into a cutting plane perpendicular to the reference axis.

[0038] [Fig.7] The [Fig.7] illustrates the nut comprising a twisted open recirculation channel.

[0039] [Fig.8A] Fig.8A illustrates a nut recirculation channel, seen in a cutting plane perpendicular to the reference axis, at one end of said recirculation channel.

[0040] [Fig.8B] Fig.8B illustrates the nut recirculation channel, seen in a cutting plane perpendicular to the reference axis, at another end of said recirculation channel.

[0041] [Fig.8C] The [Fig.8C] illustrates the nut recirculation channel, seen in a cutting plane perpendicular to the reference axis, axially at the center of said recirculation channel.

[0042] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of implementation methods

[0043] Figures 1 to 7 illustrate a ball screw mechanism 1 of a brake actuator mechanism. The ball screw mechanism 1 comprises two threaded components, namely a screw 10 and a nut 12, aligned on a reference axis 100 of the ball screw mechanism 1, which is also a reference axis of the nut 12 and the screw 10, and of the balls 14.

[0044] The screw 10 is preferably metallic, for example steel, and has a screw thread 16 which forms an internal helical raceway 18 around the reference axis 100, the internal helical raceway 18 being rotated radially in the opposite direction to the reference axis 100.

[0045] The nut 12 comprises a nut body 20, preferably metallic, for example steel, and generally cylindrical in shape. The nut body 20 has an inner annular face 22, facing the reference axis 100, and an outer annular face 24, facing away from the reference axis 100.

[0046] The inner annular face 22 has a nut thread 26 extending between two annular end bearing surfaces 48. The nut thread 26 forms an external helical raceway 116 around the reference axis 100, which is radially oriented towards The interior. The external helical raceway 116 has a bottom 32 and two opposing sides formed by the nut thread 26. The external helical raceway 116 has a characteristic rolling radius of curvature Rcr, measured in any plane perpendicular to the nut thread 26, locally at a contact zone with balls 14. The bottom 32 is radially further from the reference axis 100 than the nut thread 26, and located at a constant distance from the reference axis 100, thus forming a helix located on a cylinder of the bottom 102 centered on the reference axis 100. The external helical raceway 116 is obtained, for example, by continuous turning between two ends 46 of the external helical raceway 116.

[0047] Each of the two ends 46 of the outer helical raceway 116 has a guide wall 28, configured to guide the balls 14 between the outer helical raceway 116 and a guide channel 44 described below. The guide wall 28 projects radially towards the reference axis 100 relative to the bottom 32, the projection having a diameter substantially identical to a thread diameter of the nut 26. The guide wall 28 is concave, so as to guide the balls 14 between the outer helical raceway 116 and the guide channel 44. The inner annular face 22 further has a positioning surface 36, configured to accommodate an added part, a scoop 202 for example. The positioning surface 36 is preferably constituted by a portion of the annular end span 48 of the inner annular face 22 adjacent to the guide wall 28.Also, the inner annular face 22 has, at its two axially opposite ends, an annular lateral bearing surface 49 configured to determine a position for using the added part in axial stop.

[0048] The outer annular surface 24 is cylindrical and axially traversed by a recirculation channel 38 connected to the two ends 46 of the outer helical raceway 116 by two guide channels 44. The outer helical raceway 116 has axial symmetry with respect to an axis of symmetry 108 which is also an axis of symmetry for the recirculation channel 38, the two guide channels 44 being symmetrical to each other with respect to this axis of symmetry 108. The description that can be given of a geometric characteristic of a portion of the recirculation channel 38, of a guide channel 44 or of the outer helical raceway 116 will therefore be transposable by symmetry to the symmetrical portion along the axial symmetry.

[0049] The guide channels 44 are configured to guide the balls 14 in both directions of circulation between the recirculation channel 38 and the external helical raceway 116 and each consists of a bore 42. The guide channel 44 includes a bore 42 extending from one end 40 of the channel. recirculation 38 to one end 46 of the outer helical raceway 116. The drilling 42 is made along a drilling axis 106, and is a uniaxial cylindrical through hole extending between the recirculation ends 40 of the outer annular face 24 and the associated guide wall 28 of the inner annular face 22.

[0050] The bore 42 has an inner diameter Dp. The inner diameter Dp is greater than a diameter Db of the balls 14 so that the ratio is greater than 1.02, preferably greater than 1.05, and less than 1.1. In addition, the inner diameter Dp is less than twice the characteristic rolling radius of curvature Rcr so that the ratio is greater than 1 and less than 1.2, preferably less than 1.09.

[0051] The bore 42 has a radial component, an orthoradial component and an axial component, all three non-zero. More particularly, in projection onto a plane perpendicular to the reference axis 100 illustrated in [Fig.4], the bore 42 forms with a first line DI orthoradially tangent to the bottom cylinder 102 and passing through an internal point of intersection PI between the bore axis 106 and the bottom cylinder 102, an internal angle Al greater than 25°, preferably greater than 33°, and less than 45°, preferably less than 37°.

[0052] The recirculation channel 38 is located radially at a distance outside the raceway 116 of the nut 12 and preferably spans several turns. The recirculation channel 38 is of the open type, that is to say, it forms a groove on the outer surface 24 of the nut 12. The recirculation channel 38 extends between two axially opposed recirculation ends 40.

[0053] The recirculation channel 38 has a channel bottom wall 39 formed in the nut body 20, which extends axially between the two recirculation ends 40 and transversely between two flanks 39' of the recirculation channel 39. The channel bottom wall 39 preferably has, in any cutting plane perpendicular to the reference axis 100, a constant radius of curvature Rcc independent of the cutting plane, and a center of curvature C positioned on a central axis 107 of the recirculation channel 38, parallel to the reference axis 100. The radius of curvature Rcc is determined as a function of a ball diameter Db to be integrated into the ball screw mechanism 1. It is greater than half the ball diameter Db, and preferably less than 0.55 times the ball diameter Db.It is preferably substantially equal, within 5%, to half the internal diameter Dp of the bore 42 and preferably less than the characteristic rolling radius of curvature Rcr so that the ratio S2L is greater than 1 and less than Rcc. at 1.2, preferably less than 1.08.

[0054] In any cutting plane perpendicular to the reference axis 100, the two sides 39' of the recirculation channel 39 are symmetrical to each other on either side of a median axis 110 passing through the center of curvature C of the bottom wall of the channel 39. The median axis 110 has, with a radial axis 111 passing through the center of curvature C, a recirculation angle A3. The recirculation angle A3 varies as a function of an axial abscissa of the cutting plane, measured along the central axis of the recirculation channel 38 as shown in Figures 8A, 8B, and 8C. The recirculation angle A3 varies according to a continuously increasing or continuously decreasing function, preferably linear, for example, with a constant derivative. The function that the recirculation angle A3 follows has a value of zero in a plane perpendicular to the reference axis 100 and containing an axis of symmetry of the recirculation channel 108' (see [Fig. 8C]).At the two extreme abscissas, in other words, in a cutting plane perpendicular to the reference axis 100 located at the end of the recirculation channel 38, the median axis 110 is parallel to the drilling axis 106, within 5° (see Figures 8A and 8B). In this way, the balls 14 can pass smoothly between the recirculation channel 38 and the guide channel 44. The angular variation of the recirculation angle A3 between the two ends of the recirculation channel 38 is preferably greater than 45°, and even greater than 60°.

[0055] The recirculation channel 38 is preferably obtained by machining with a tool, preferably a milling cutter, penetrating through the outer annular face 24 of the nut body 20 and progressing linearly along the axis 107 while pivoting around this axis 107 as it progresses, according to the function defined for the recirculation angle A3.

[0056] In any cutting plane perpendicular to the reference axis 100, a point on the bottom wall of the channel 39 can be determined that is closest to the reference axis 100 and located at a distance from the reference axis 100 that does not vary with the cutting plane considered, so that a bottom cylinder of the channel 105 centered on the reference axis 100 and containing said point in each cutting plane can be defined. Preferably, the points on the bottom wall of the channel 39 closest to the reference axis 100 in the different cutting planes perpendicular to the reference axis 100 are located on a straight bottom line of the channel 104 parallel to the reference axis 100.

[0057] In any cross-sectional plane perpendicular to the reference axis 100, the two sides 39' preferably form two straight segments 41 which may be flared or, preferably, parallel to each other. The two segments 41 are then located at a distance from each other equal to twice the radius of curvature of the bottom wall of the channel 39, so as to allow the passage of the balls 14 in the recirculation channel 38.

[0058] In an alternative embodiment, the recirculation channel may have a non-straight shape, for example a spiral.

[0059] An external intersection point P2 can be defined between the drilling axis 106 and a channel center cylinder 105' centered on the reference axis 100 and having a diameter equal to the sum of the diameter of the channel bottom cylinder 105 and the ball diameter Db. Viewed in projection onto a longitudinal plane (illustrated in [Fig.5]) comprising the reference axis 100 and the external intersection point P2, the drilling axis 106 forms, with a generatrix of the channel center cylinder 105' in this plane, an external angle A2 greater than 45°, preferably greater than 55°, and less than 75°, preferably less than 65°.

[0060] Alternatively, the cylinder with channel center 105' centered on the reference axis 100 can be defined as the cylinder containing on its surface the centers of curvature C and the axis 107.

[0061] Optionally, as particularly illustrated in Figures 1, 2, and 6, the nut 12 may include one or more attached deflectors 200. The deflector 200 is configured to facilitate the guidance of the balls 14 between the outer helical raceway 116 and one of the guide channels 44. In an operating position, the deflector 200 is positioned at the end 46 of the outer helical raceway 116. More specifically, the deflector 200, which may be a scoop 202, for example, has a bearing surface 204 intended to bear against the positioning surface 36 of the nut 12. The deflector 200 also includes an extension surface 206, intended to extend the guide wall 28 of the nut 12.

[0062] The extension surface 206 extends the guide wall 28 tangentially and continuously, so as to smoothly guide the balls 14 between the outer helical raceway 116 and the associated guide channel 44. The extension surface 206 has an overall spherical cap shape with a radius of curvature configured for guiding the balls 14. The extension surface 206 forms a radial projection towards the reference axis 100 so as to have a smaller distance from the reference axis 100 than the distance between the nut thread 26 and the reference axis 100, and preferably, so as to penetrate the inner helical raceway 16 without contacting it when the ball screw mechanism 1 is ready for use, i.e., mounted.

[0063] The deflector 200 is a component of a seal 300. The seal 300 is preferably made of plastic, so that it is a single piece and can be manufactured by molding without undercuts, thus reducing manufacturing time and costs. The plastic may be conventional, partially or fully recycled, and / or fully or partially bio-based. The plastic may also be reinforced with organic or inorganic, natural or synthetic additives, such as fiberglass. For example, the 300 seal can, if necessary, be made from other materials, such as metal, possibly with a machining and / or sintering step, and if required, be composed of several parts. A multi-grade and / or multi-material design is also possible.

[0064] The seal 300 is configured to fit into the nut body 20. The seal 300 has an annular body 301, comprising an outer annular surface 302, configured to bear, by shrink fitting, on the annular end bearing surface 48. The annular body 301 also comprises an inner annular surface 304, opposite the outer annular surface 302. The inner annular surface 304 has a sealing lip 306 extending radially inwards from the inner annular surface 304. The sealing lip 306 is configured to retain a lubricant element of the brake actuator mechanism, for example grease. The sealing lip 306 forms a counter-form of the internal helical bearing race 16 of the screw 10, in particular of homothetic type, without coming into contact with the screw 10. The sealing lip 306 extends over at least 1 / 2 turn of the propeller, preferably at least 3 / 4 of a turn of the propeller, without making a complete turn of the propeller.

[0065] Furthermore, the annular body 301 of the seal 300 includes a lateral annular surface 308, positioned towards the inside of the nut 12, i.e. with regard to the outer helical raceway 116. The lateral annular surface 308 has a positioning tab 310 projecting axially from the lateral annular surface 308 towards the outer helical raceway 116. The positioning tab 310 has at one end the deflector 200, the positioning tab 310 extending between the lateral annular surface 308 and the deflector 200.

[0066] When the seal 300 is forcibly inserted into the nut 12, the seal 300 is positioned so that the position of the deflector 200 corresponds to its position of use, i.e. that its bearing surface 204 is in contact with the positioning surface 36 of the nut 12. The seal 300 is then shrunk to the inner annular face 22 and a portion of the lateral annular surface 308 butts axially against the lateral annular bearing surface 49 of the nut 12.

[0067] The brake actuator mechanism as described further includes a sleeve 400, configured to contact the outer annular face 24 of the nut 12, and, where appropriate, close the open recirculation channel 38. The sleeve 400 also allows, if necessary, the ball screw mechanism 1 to be provided with desired properties that cannot be provided by the nut 12. For example, the sleeve 400 can undergo a surface treatment incompatible with an initial treatment applied to the nut 12, allowing the nut 12 to exhibit hardness properties, for example, while the sleeve 400 exhibits corrosion-resistant properties. The treatments can vary and depend on the needs according to the environment to which the ball screw mechanism 1, and more generally the brake actuator mechanism, will be subjected.

[0068] Naturally, the examples shown in the figures and discussed above are given by way of illustration only and are not intended to be limiting. It is explicitly intended that the different embodiments illustrated may be combined to propose others.

[0069] According to an unillustrated variant, the deflector 200 is fixedly attached to the nut 12 by means of a pin, which can be positioned below the bearing surface 204, for example, and is designed to fit into a hole formed in the positioning surface 36 of the associated nut 12. The deflector 200 can then be attached to the nut 12 without necessarily being connected to the seal 300.

Claims

1. Demands A ball screw mechanism nut (12) defining a reference axis (100) and comprising a nut body (20), the nut body (20) having an outer annular face (24) facing away from the reference axis (100), an inner annular face (22) facing the reference axis (100), on which is formed a nut thread (26) delimiting an outer helical raceway (116) for balls (14) of the ball screw mechanism (1), a recirculation channel (38) located radially outside the outer raceway (24), and two guide channels (44), each configured to guide the balls (14) between an associated end (46) of the outer helical raceway (116) of the nut thread (26) and an associated end (40) of the recirculation channel (38), the raceway having symmetry axial with respect to an axis of symmetry (108) perpendicular to the reference axis (100),the recirculation channel (38) having axial symmetry with respect to the axis of symmetry (108), the two guide channels (44) being symmetrical to each other with respect to the axis of symmetry (108), characterized in that the recirculation channel (38) is open on the outer annular face (24) and has, - a channel bottom wall (39) which, in any cross-sectional plane perpendicular to the reference axis (100), has a constant radius of curvature and a center of curvature positioned on a central axis (107) of the recirculation channel (38), parallel to the reference axis (100) and - two sides (39') continuous with the bottom wall of the channel (39) and which, in any plane of section perpendicular to the reference axis (100), are symmetrical to each other on either side of a median axis (110) passing through the center of curvature, the median axis (110) making, with a radial axis (111) passing through the center of curvature, a recirculation angle (A3) which varies according to an axial abscissa of the plane of section, measured along the central axis (107) of the recirculation channel (38), according to a continuously increasing or continuously decreasing function, preferably linear, preferably with a constant derivative, preferably passing through r a zero angle value in a plane containing the axis of symmetry (108).

2. Nut (12) according to claim 1, characterized in that in any cutting plane perpendicular to the reference axis (100), the two flanks (39') are made up of two straight segments, preferably parallel to each other and to the median axis (110).

3. Nut (12) according to any one of the preceding claims, characterized in that in any cutting plane perpendicular to the reference axis (100), the bottom wall of the channel (39) forms a semicircle.

4. Nut (12) according to any one of the preceding claims, characterized in that each of the two guide channels (44) is constituted by a uniaxial bore oriented along a bore axis (106), the bore axis (106) having a projection onto an end cutting plane intersecting the associated end (40) of the recirculation channel (38), which is parallel to within 5°, to the median axis (110) located in the end cutting plane.

5. Nut (12) according to claim 3 or 4, characterized in that, viewed in projection onto a plane perpendicular to the reference axis (100), the drilling axis (106) forms an internal angle (Al) greater than 25°, preferably greater than 33°, and less than 45°, preferably less than 37° with a tangent (Dl) to a bottom track cylinder (102) on which is located a helical bottom (32) of the external helical rolling track (116) and passing through an internal intersection point (PI) between the drilling axis (106) and the bottom track cylinder (102).

6. Nut (12) according to any one of claims 4 and 5, characterized in that the recirculation channel (38) has a channel bottom line (104) located on a channel bottom cylinder (105) centered on the reference axis (100) and having a predetermined diameter, and the drill shaft (106) has an external intersection point (P2) with a channel center cylinder (105') centered on the reference axis (100) and having a diameter equal to the sum of the diameter of the channel bottom cylinder (105) and the ball diameter (Db), and in that, viewed in projection onto a longitudinal plane comprising the reference axis (100) and the external intersection point (P2), the drill shaft (106) forms an external angle (A2) greater than 45°, of preferably greater than 55°, and less than 75°, preferably less than 65°, with the center channel cylinder (105').

7. Nut (12) according to claim 6, characterized in that the bottom line of the channel (104) is straight and parallel to the reference axis (100).

8. Nut (12) according to any one of the preceding claims, characterized in that the nut body (20) comprises, at the end (46) of the external helical raceway (116), a concave guide wall (28), projecting radially towards the reference axis (100) relative to the bottom (32) of the external helical raceway (116), joining without an edge the guide channel (44) with a flank of the external helical raceway (116), and for guiding the balls (14) between the guide channel (44) and the external helical raceway (116).

9. Nut (12) according to claim 8, characterized in that it comprises an added deflector (200), a scoop (202) for example, comprising a bearing surface (204) intended to bear against a positioning surface (36) in tangent and continuous contact with an annular end bearing surface (48) of the nut (12), and an extension surface (206), intended to extend the guide wall (28) of the nut (12), located in the extension of the bore opposite the external helical bearing race (116).

10. Nut (12) according to claim 9, characterized in that the deflector (200) includes a positioning tab (310) intended to bear fixedly against the inner annular surface (22) of the nut (12).

11. Nut (12) according to any one of claims 9 and 10, characterized in that the extension surface (206) has an overall spherical cap shape.

12. Nut (12) according to any one of claims 10 and 11, characterized in that the deflector (200) is a constituent part of an annular seal (300) attached to the nut (12), the deflector (200) being fixedly connected, via the positioning tab (310), to said annular seal (300).

13. Nut (12) according to claim 12, characterized in that the annular seal (300) comprises an annular body (301) about the reference axis (100) of the nut (12) intended to be aligned with a helix axis of the nut (12), the annular body (301) comprising a outer annular surface (302) bearing against the nut (12), preferably against the inner annular face (22), in a bearing direction having a radial component with respect to the reference axis (100).

14. Nut (12) according to claim 13, characterized in that the annular seal (300) comprises a seal lip (306) extending radially inwards from the annular body of the seal (300).

15. Nut (12) according to claim 14, characterized in that the sealing lip (306) makes at least 1 / 2 helix turn, preferably at least 3 / 4 helix turn.

16. Nut (12) according to any one of claims 13 to 15, characterized in that the positioning tab (310) of the deflector (200) is fixedly linked to the annular body of the annular seal (300), the deflector (200) being axially projecting relative to the annular body (301).

17. Nut (12) according to any one of the preceding claims, characterized in that it comprises another guide channel (44), configured to guide the balls (14) between another end (46) of the outer helical raceway (116) of the nut thread (26) opposite the end (46) of the outer helical raceway (116) of the nut thread (26) and another recirculation end (40) of the recirculation channel (38) opposite the recirculation end (40) of the recirculation channel (38), by direct contact with the balls (14), and comprises another oriented bore, preferably along another bore axis (106) which has a radial component identical to that of the bore axis (106), and, preferably still, an orthoradial component and an axial component, both opposite to those of the bore axis (106),the other bore opening onto the inner annular face (22) at the other rolling end (46) of the outer helical raceway (116) and onto the outer annular face (24) at the other recirculation end (40) of the recirculation channel (38).

18. Nut device characterized in that it comprises a nut (12) according to any one of the preceding claims and a sleeve, the sleeve (400) being configured to come into contact with the outer annular face (24) of the body of the nut (20), and where appropriate close the open recirculation channel (38).

19. Ball screw mechanism (1), in particular for a brake actuator, characterized in that it comprises a nut (12) according to one any of claims 1 to 17 or a nut device according to claim 18, a screw and balls circulating between an inner helical raceway (16) formed by the screw (10) and the outer helical raceway (116) of the nut (12), the nut (12) and / or the sleeve (400) and / or the screw preferably forming a piston configured to actuate the brake.

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