End recirculator for ball screw mechanism

Abstract

Recirculator (30) for a nut (12) of a ball screw mechanism (1), comprising an annular body (32) having a reference axis (300) intended to be aligned with a helix axis of the nut (12), the annular body (32) comprising a bearing surface (36) configured to bear against a nut (12) of the ball screw mechanism (1) in a bearing direction having an axial component parallel to the reference axis (300), and a guide structure (34) configured to guide balls in a recirculation path opening at a first guide end (62) into a recirculation channel of the nut (12) and at a second guide end (72) onto a raceway (116) defined by a thread of the nut (12), characterized in that the bearing surface (36) is at least partially located in a cutting plane (130) cutting the recirculation trajectory and perpendicular to the reference axis (300). (Abstract Figure: 1)

Description

Title of the invention: End recirculator for ball screw mechanism TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the technical field of ball screws, and more particularly to ball screw recirculators whose recirculation is external. STATE OF THE PRIOR ART

[0002] In document CN 217481881 a ball screw mechanism is presented, the external recirculation of the balls of which is carried out by means of two end recirculators positioned at the two ends of the nut, and connected by a recirculation channel parallel to the axis of the screw. The end recirculators disclosed in this document have, in addition to their ability to redirect the balls during their recirculation through a recirculation channel, the characteristic of retaining the grease inside the annular space located between the nut and the screw.

[0003] One of the disadvantages of such end recirculators is the axial bulk they generate, since the two functions of guiding the balls and retaining the grease are performed by zones axially distant from each other. These recirculators can therefore only be used in ball screw mechanisms whose applications do not require extensive optimization of the spatial bulk. Statement of the invention

[0004] The invention aims to overcome the drawbacks of the state of the art and to propose a compact and simple solution for carrying out the recirculation of a ball screw mechanism.

[0005] To this end, according to a first aspect of the invention, a recirculator for a nut of a ball screw mechanism is proposed, the recirculator comprising an annular body around a reference axis of the recirculator intended to be aligned with a helix axis of the nut, the annular body comprising a bearing surface configured to bear against a nut of the ball screw mechanism in a bearing direction having an axial component parallel to the reference axis, and a guide structure configured to guide balls in a recirculation path having a first guide end configured to open into a recirculation channel of the nut and a second guide end configured to open onto a raceway defined by a thread of the nut, the bearing surface being at least partially located in a section plane intersecting the recirculation path and perpendicular to the reference axis,remarkable in, that the annular body includes a seal lip extending radially inwardly from the annular body of the recirculator.

[0006] The recirculator makes it possible to ensure in a restricted volume a large contact and support surface with the nut, allowing a good joint between the recirculator and the nut, and the guidance of the balls of the ball screw mechanism.

[0007] In addition, the seal lip thus makes it possible to form a counterform for a bearing path of the screw and therefore to limit leaks of a lubricant necessary for the proper functioning of the ball screw mechanism, grease for example.

[0008] According to one embodiment, the bearing surface is flat, which contributes to the compactness of the part, as well as to the simplification of the manufacture of said part. Alternatively, a truncated conical bearing surface is conceivable.

[0009] According to one embodiment, the support surface extends over an angular sector around the reference axis, which does not intersect with the recirculation trajectory. The support and guidance functions of the balls are thus distributed around the reference axis. Preferably, the angular sector has an apex angle greater than ir / 2 radians, preferably greater than 3ir / 4 radians, and less than 3ir / 2 radians, preferably less than 5ir / 4 radians, for example 7ir / 6 radians.

[0010] According to one embodiment, the guide structure projects radially outwards from the annular body.

[0011] According to one embodiment, the first guide end of the guide structure projects, in particular axially, relative to the annular body, to produce a curvilinear recirculation trajectory whose first guide end projects axially relative to the annular body of the recirculator, so as to open into the recirculation channel of the nut.

[0012] According to one embodiment, the second guide end of the guide structure extends on either side of the cutting plane.

[0013] According to one embodiment, the second guide end of the guide structure is formed by a scoop. Preferably, the scoop projects in a direction configured to be tangent to a raceway of the nut. In this way, the recirculator, via the scoop, allows recirculation of the balls in a fluid manner, in order to achieve a smooth transition, without shocks, between the trajectory defined by the raceway of the nut and the recirculation trajectory or a loss of efficiency.

[0014] According to one embodiment, the recirculation trajectory at the first guide end is perpendicular to the support plane.

[0015] According to one embodiment, the seal lip is helical in shape, more preferably the seal lip makes at least 1 / 2 helix turn, preferably at least 3 / 4 helix turn.

[0016] According to one embodiment, the recirculator is a single-piece unit, preferably made of plastic. The materials may be traditional plastics, partially or fully recycled plastics, or fully or partially bio-sourced. A metal production is also possible, for example by machining or sintering. Preferably, the recirculator may be molded without undercutting, which allows for manufacturing by molding and a reduction in costs related to cycle time or the complexity of producing molds or tools. Other manufacturing methods are, however, possible, in particular by additive manufacturing. A multi-grade and / or multi-material production is also not excluded.

[0017] According to another aspect of the invention, the latter relates to a ball screw mechanism comprising a screw, having an inner helical raceway and a central axis; a nut, having an outer helical raceway and a recirculation channel; at least two balls arranged between the inner helical raceway of the ball screw and the outer helical raceway of the nut; at least one end recirculator arranged at one of the axial ends of the nut to ensure the recirculation of the balls, the end recirculator comprising a bearing surface against the nut and a guide structure for maintaining the balls in a defined recirculation path; remarkable in that the end recirculator is as described above.

[0018] According to one embodiment, the axial end has a receiving surface in contact with the bearing surface of the recirculator, the bearing surface of the recirculator and the receiving surface of the nut having complementary geometries, so that the recirculator can be connected to the nut and form a homogeneous assembly.

[0019] According to one embodiment, the axial end comprises an annular skirt projecting axially relative to the receiving surface, the annular skirt and the receiving surface delimiting a volume in which the annular body of the recirculator is housed at least partially, and preferably totally, which allows the recirculator to be inserted axially into the nut, protected by the latter, and improves the compactness and connection of the assembly formed by the nut and the recirculator.

[0020] According to one embodiment, the annular axial end has a radial notch in the continuity of the recirculation channel in order to house the guide structure in a guide zone when the guide structure is in the position of use, and to not have any element projecting relative to the external surface of the nut excluding the risks of snagging during handling or loss of radial compactness.

[0021] According to one embodiment, the notch forms a reception zone forming at least one guide face allowing smooth recirculation of the balls between the recirculation channel and the recirculator.

[0022] Naturally, the ball screw mechanism can be equipped with two recirculators according to the first aspect of the invention, located at the two axial ends of the nut.

[0023] According to a particularly advantageous embodiment, the end recirculator comprises one or more guide faces facing one or more guide faces of the nut to delimit the recirculation path between the two ends. By using the end recirculator and the nut to delimit the recirculation path, the mechanism is made more compact. BRIEF DESCRIPTION OF THE FIGURES

[0024] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures. • [Fig.l] [Fig.l] illustrates a ball screw mechanism comprising a screw, a nut and two end recirculators. • [Fig.2] [Fig.2] illustrates an isometric perspective view of the nut. • [Fig.3A] [Fig.3A] illustrates an isometric perspective view of the end recirculator. • [Fig.3B] [Fig.3B] illustrates a bottom view of the end recirculator. • [Fig.3C] [Fig.3C] illustrates a front view of the end recirculator. • [Fig.3D] [Fig.3D] illustrates a view of the rear of the recirculator end. • [Fig.3E] [Fig.3E] illustrates a top view of the end recirculator. • [Fig.4] [Fig.4] illustrates an axial section of the ball screw mechanism.

[0025] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of embodiments

[0026] In [Fig.l] is illustrated a ball screw mechanism 1 comprising two threaded components, namely a screw 10 and a nut 12, balls as well as two end recirculators 30, all aligned on a reference axis 100 of the ball screw mechanism 1, which is aligned with a reference axis 110 of the screw 10, a reference axis 120 of the nut 12 and a reference axis 300 of each of the two end recirculators 30.

[0027] The ball screw mechanism 1, as illustrated in Figures 1 and 4, without the balls, has an axis of symmetry 400 perpendicular to the axis 100, so that the description which will be made of the recirculator 30 at one end of the nut 12 will be transposable to the recirculator 30 at the opposite end of the nut. But this symmetry is a simple option, and is not limiting.

[0028] The screw 10 is preferably metallic, for example made of steel, and has a screw thread 14 which forms an internal helical raceway 16 around the reference axis 110 of the screw 10, the internal helical raceway 16 being turned radially away from the reference axis 110.

[0029] The nut 12, illustrated in detail in Figures 2 and 4, is preferably metallic, for example steel, and is generally cylindrical in shape. The nut 12 has a nut thread 114 which forms an outer helical raceway 116 around the reference axis 120, facing radially inwards, and an outer surface 25 facing radially outwards. The outer surface 25 is cylindrical and axially traversed by a recirculation channel 18. The recirculation channel 18 is located radially at a distance from the raceway 116 of the nut 12 and preferably spans several turns thereof.In this embodiment, the recirculation channel 18 is of the open type, in other words, it forms a groove on the outer surface 25 of the nut 12, but this configuration is optional, and it is alternatively possible to provide a recirculation channel 18 that is totally or partially closed at its outer radial periphery, depending on the production requirements.

[0030] The nut 12 further has two axial ends 20 opposite two opposite axial ends of the recirculation channel 18. Each of the axial ends 20 is annular and has a receiving surface 22 and an annular skirt 24, axially projecting outwardly relative to the receiving surface 22. The skirt 24 has a diameter slightly smaller than the diameter of the outer surface 25, which can for example be used for fixing a fixing flange for a member secured to the nut 12, or for fixing a sealing bellows. The skirt 24 has an inner annular face 74 facing radially towards the reference axis 120. The receiving surface 22 as well as the skirt 24 are configured to accommodate the end recirculator 30 and delimit a housing volume of the end recirculator 30.Each axial end 20 has a radial notch 26, limited by the plane 118 at the end of the recirculation channel 18, this notch 26 splitting the skirt 24 so that it forms only a cylindrical arc. The notch 26 generates a reception zone 40 whose shape corresponds to a counter-shape of a guide structure 34 of the end recirculator 30, which will be described below.

[0031] In another embodiment, the recirculation channel 18 is closed, in other words it is integrated into the nut 12. Where appropriate, the notch 26 does not split the entire skirt 24 so that said skirt 24 is annular.

[0032] The receiving zone 40, formed in the nut 12 by the notch 26, comprises two support flats 42 on either side of a first guide face 44 of the nut 12 connected to the recirculation channel 18, as well as a second guide face 45 and a scoop support 46.

[0033] The receiving surface 22 forms a planar annular arc around the reference axis 120, extending from the notch 26 over an angular sector with an apex angle greater than ir / 2 radian, preferably greater than 3ir / 4, and less than 3ir / 2, preferably less than 5ir / 4, for example 7ir / 6, in a clockwise direction 210 or counterclockwise direction 220 so as to form a counter-shape of a bearing surface 36 described below.

[0034] The end recirculators 30 are preferably made of plastic material, in order to be a single piece while being able to be manufactured by molding without undercutting, which makes it possible to reduce the manufacturing times of the part and to reduce costs. The plastic material may be a traditional plastic, a partially or totally recycled plastic and / or totally or partially bio-sourced. The end recirculators 30 may however, if necessary, be made of other materials, metal for example, if necessary with a machining and / or sintering step, and if necessary be composed of several parts. A multi-grade and / or multi-material production is also not excluded.

[0035] The two end recirculators 30 are identical, and have an annular body 32 as well as a guide structure 34, the guide structure 34 projecting radially outwards, and axially towards the nut 12, relative to the annular body 32.

[0036] The annular body 32, illustrated in detail in FIGS. 3A, 3B, 3C, 3D and 3E, has an outer annular face 76 facing radially outwards and an inner annular face 78 facing radially towards the reference axis 300. In addition, the annular body 32 comprises a flat bearing surface 36 in a bearing plane 130 and is configured to bear against the nut 12, at the receiving surface 22, when the end recirculator 30 is in the use position. The bearing surface 36 is in the form of a planar annular arc extending over an angular sector around the reference axis 300, with an apex angle greater than ir / 2 radian, preferably greater than 3ir / 4, and less than 3ir / 2, preferably less than 5ir / 4, for example 7ir / 6, extending from the guide structure 34 in a clockwise direction 210.The annular body 32 further has a seal lip 38 extending radially inward from the annular body 32 of the end recirculator 30. The seal lip 38 is arranged on the inner annular face 78 of the recirculator 30 and forms a counter-shape of the inner helical raceway 16, in particular of the homothety type, without coming into contact with the screw 10.

[0037] The guide structure 34 has a positioning body 58 and a scoop 48 which form an open conduit 70 for guiding the balls along a curvilinear trajectory between a first guide end 62, open onto the recirculation channel 18 and a second guide end 72 open onto the raceways 16, 116 of the screw 10 and the nut 12.

[0038] The first guide end 62 projects axially relative to the cutting plane 130, while the second guide end 72 projects “obliquely” between the raceways 16, 116 of the screw 10 and the nut 12. Furthermore, the second guide end 72 is cut by the cutting plane 130.

[0039] More specifically, the positioning body 58 has an outer wall 60, two side walls 64, two transverse walls 66 and an inner wall 68. The outer wall 60 is arranged radially outside the other walls, while the inner wall 68 is arranged radially inside the other walls. One of the two transverse walls 66 overlaps the annular body 32, while the other transverse wall, illustrated in [Fig. 3A], projects axially relative to the section plane 130 and forms the first guide end 62, intended to open onto the recirculation channel 18. The positioning body 58 has a guide notch 54 open on the outer wall 60 at the first guide end 62 when the recirculation channel 18 is, as in the present case, open.

[0040] The scoop 48 forms the second guide end 72 of the open guide duct 70 and is configured to open onto the raceways 16, 116 of the screw 10 and the nut 12, and to fluidly redirect the balls from the recirculating channel 18 to the raceways 16, 116 of the screw 10 and the nut 12 and vice versa. To do this, the scoop 48 is oriented radially and orthoradially, in order to guide the balls towards the recirculating channel 18 or the raceways 16, 116, with, where appropriate, a minimal axial component so that the guidance of the balls by the scoop 48 is tangent to the helical raceways 16, 116. The scoop 48 has a guide face 50, configured to orient the balls during their recirculation, and a rear face 52, arranged opposite the guide face 50.The guide face 50 is a groove whose profile may be, for example, an arc of a circle or an ogive, which defines a recirculation path between the two ends 62, 72 of the groove. The scoop 48 is cut by the support plane 130. Remarkably, the guide faces 44, 45 of the nut 12 face the guide face 50 of the recirculator, so that the recirculation path is delimited, over its entire path between the two ends 62, 72 of the groove, by the guide face 50 of the end recirculator 30 and the first and second guide faces 44, 45 of the nut 12.

[0041] The seal lip 38 extends from the scoop 48, on the inner annular face 78 of the end recirculator 30, taking shape at the rear face 52 of the scoop 48 in the same clockwise rotation direction 210 as the bearing surface 36, i.e. in the clockwise direction 210, over at least 1 / 2 propeller turn, preferably at least 3 / 4 propeller turn, without making a complete propeller turn. The seal lip 38 is cut by the bearing plane 130.

[0042] The guide structure 34 and the annular body 32 are respectively complementary to the receiving zone 40 and the receiving surface 22 of the nut 12.

[0043] The balls may for example be made of steel or ceramic, and are sized and positioned to circulate in a closed circuit between the outer helical raceway 11 6 of the nut 12 and the inner helical raceway 16 of the screw 10, between the guide face 50 of each end recirculator 30 and the first and second recirculation faces 44, 45 of the nut 1 2 and in the recirculation channel 18, preferably without separators between the balls.

[0044] During assembly, the end recirculators 30 are inserted axially into the nut 12, one end recirculator 30 at each of the two axial ends 20, which allows the ball screw mechanism 1 to become more compact. In the remainder of the description of the assembly, we will detail the positioning of a single end recirculator 30, this description naturally applying to the second end recirculator 30. The end recirculator 30 is inserted axially by force into the axial end 20, the annular body 32 being shrunk to the inner annular face 74, so as to be in the position of use when the bearing surface 36 of the end recirculator 30 abuts against the receiving surface 22. The bearing surface 36 is then in contact with the receiving surface 22 while the annular face 76 of the end recirculator 30 is in contact with the annular inner face 74 of the skirt 24.The sealing lip 38 extends the helical pattern of the thread of the nut 12. .

[0045] In addition, the guide structure 34 is housed in the receiving zone 40 and is in contact with the nut 12. More precisely, the inner wall 68 comes into contact and rests on the support flats 42, the two side walls 64 as well as one of the two transverse walls 66 are in contact with the nut 12, the scoop 48 rests in contact on the scoop support 46, and at the first guide end 62, the scoop 48 opens into tangential contact on the second guide face 45 of the nut 12, itself opening onto the first guide face 44 which opens onto the recirculation channel 18. The guide faces 44, 45 of the nut 12 allow a transition from the recirculation channel 18 to the scoop 48 of the end recirculator 30 and conversely, allowing a smooth recirculation path between the recirculation channel 18 and the end recirculator 30.

[0046] The screw 10 can be inserted into the assembly formed by the nut 12 and the two end recirculators 30 by screwing. The sealing lip 38 penetrates the inner helical raceway 16, without coming into contact, and makes it possible to minimize the leakage of lubricant into the ball screw mechanism 1, grease for example. The balls can then be inserted into the ball screw mechanism 1 one by one through the recirculation channel 18. The balls travel in the raceways 16, 116 helicals passing through the end recirculators 30. The ball screw mechanism 1, illustrated in [Fig.4], is then closed by a sleeve shrunk to the outer surface 25 of the nut 12, allowing the recirculation channel 18 to be closed.

[0047] The examples shown in the figures and discussed above are given for illustrative purposes only. Other embodiments may be envisaged, in particular by combining the characteristics of the different illustrated embodiments.

[0048] For example, the end recirculator 30 may have, at the level of the bearing face 36, a stud comprising a chamfer and a lip, allowing it to snap into a corresponding counter-form located in the receiving face 22 of the nut 12.

Claims

Claims

1. A recirculator (30) for a nut (12) of a ball screw mechanism (1), the recirculator (30) comprising an annular body (32) about a reference axis (300) of the recirculator (30) intended to be aligned with a helix axis of the nut (12), the annular body (32) comprising a bearing surface (36) configured to bear against a nut (12) of the ball screw mechanism (1) in a bearing direction having an axial component parallel to the reference axis (300), and a guide structure (34) configured to guide balls in a recirculation path having a first guide end (62) configured to open into a recirculation channel of the nut (12) and a second guide end (72) configured to open onto a raceway (116) defined by a thread of the nut (12),the bearing surface (36) being at least partially located in a section plane (130) intersecting the recirculation path and perpendicular to the reference axis (300), characterized in that the annular body (32) comprises a seal lip (38) extending radially inwards from the annular body (32) of the recirculator (30).,

2. Recirculator (30) according to claim 1, characterized in that the bearing surface (36) is flat.

3. Recirculator (30) according to any one of the preceding claims, characterized in that the bearing surface (36) extends over an angular sector around the reference axis (300), which is without intersection with the recirculation trajectory.

4. Recirculator (30) according to claim 3, characterized in that the angular sector has an apex angle greater than ir / 2 radians, preferably greater than 3ir / 4 radians, and less than 3ir / 2 radians, preferably less than 5ir / 4 radians, for example 7ir / 6 radians.

5. Recirculator (30) according to any one of the preceding claims, characterized in that the guide structure (34) projects radially outwards from the annular body (32).

6. Recirculator (30) according to any one of the preceding claims, characterized in that the first guide end (62) of the guide structure (34) projects, in particular axially, relative to the annular body (32).

7. Recirculator (30) according to any one of the preceding claims, characterized in that the second guide end (72) of the guide structure (34) is formed by a scoop (48).

8. Recirculator (30) according to claim 7, characterized in that the scoop (48) projects in a direction configured to be tangent to a raceway (116) of the nut.

9. Recirculator (30) according to any one of the preceding claims, characterized in that the recirculation path at the first guide end (62) is perpendicular to the support plane (130).

10. Recirculator (30) according to any one of the preceding claims, characterized in that the seal lip (38) is of helical shape.

11. Recirculator (30) according to any one of the preceding claims, characterized in that the seal lip (38) makes at least 1 / 2 helix turn, preferably at least 3 / 4 helix turn.

12. Recirculator (30) according to any one of the preceding claims, characterized in that it is a single-piece unit, preferably made of plastic.

13. Recirculator (30) according to any one of the preceding claims, characterized in that it can be molded without undercutting.

14. Ball screw mechanism (1) comprising: - a screw (10), having an inner helical raceway (16) and a central axis (110); - a nut (12), having an outer helical raceway (116) and a recirculation channel (18); - at least two balls arranged between the inner helical raceway (16) of the ball screw (10) and the outer helical raceway (116) of the nut (12); - at least one end recirculator (30) arranged at one of the axial ends (20) of the nut (12) for ensuring the recirculation of the balls, the end recirculator comprising a bearing surface (36) against the nut (12) and a guide structure (34) for maintaining the balls in a defined recirculation path; characterized in that the end recirculator (30) is according to any one of the preceding claims.

15. Ball screw mechanism (1) according to claim 14, characterized in that the axial end (20) has a receiving surface (22) in contact with the bearing surface (36) of the recirculator (30), the bearing surface (36) of the recirculator (30) and the receiving surface (22) of the nut (12) having complementary geometries.

16. Ball screw mechanism (1) according to claim 15, characterized in that the axial end (20) comprises an annular skirt (24) projecting axially relative to the receiving surface (22), the annular skirt (24) and the receiving surface (22) delimiting a volume in which the annular body (32) of the recirculator (30) is housed at least partially, and preferably totally.

17. Ball screw mechanism (1) according to claim 16, characterized in that the annular skirt (24) has a radial notch (26) in the continuity of the recirculation channel (18).

18. Ball screw mechanism (1) according to any one of claims 15 to 17, characterized in that the end recirculator (30) comprises one or more guide faces (50) facing one or more guide faces (44, 45) of the nut (12) to delimit the recirculation path between the two ends (62, 72).

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