Threaded assembly of a ball screw mechanism, having external recirculation and internal recirculation

Abstract

The invention relates to a threaded assembly comprising a recirculating threaded member (13) of a ball screw mechanism (10), helical raceways, housing cavities (24) opening onto the helical raceways, the threaded assembly further comprising at least one recirculation channel (32) opening into two consecutive housing cavities (24) from among the housing cavities (24), the two consecutive housing cavities opening onto a raceway with multiple turns (18B) from among the helical raceways, deflectors forming at least two external recirculation paths (36) each opening onto the recirculation channel (32) and the helical raceway with multiple turns (18B), characterised in that the recirculation paths further include at least one internal recirculation path (34) turned in the radial reference direction (300) and opening onto the same internal recirculation turn of an internal raceway (18A) from among the raceways.

Description

Threaded assembly of a ball screw mechanism, featuring external and internal recirculation TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a ball screw mechanism, and more specifically to a ball screw mechanism equipped with recirculators for guiding balls through at least one turn of a thread in said mechanism. It also relates to a threaded assembly for such a ball screw mechanism. PREVIOUS STATE OF THE ART

[0002] Ball screws are particularly efficient mechanical devices for transmitting linear and rotary motion, used in various fields such as aerospace, robotics, and automotive. Their operating principle is based on the interposition of balls between the screw's threaded shaft and a nut. Thanks to this system, ball screws offer superior efficiency compared to traditional screw-nut devices, minimizing friction while allowing them to support significant loads.

[0003] Ball screws are primarily classified into two types, depending on how the closed-loop circulation of the balls within the mechanism is achieved. In internal recirculation mechanisms, the balls follow a helical path for slightly less than one revolution between the two threaded members. They are then deflected from one end of this helical path to the other by a recirculator attached to one of the threaded members, called the recirculation threaded member. This recirculation member allows the balls to pass through a thread of the other threaded member without losing contact with it. The resulting recirculation path is described as S-shaped due to its contour.In so-called external recirculation mechanisms, the balls follow a helical path over several turns between the two threaded components. At the recirculating threaded component, a recirculation channel causes the balls to lose contact with the other threaded component of the mechanism, forcing them to pass over several turns in a recirculation channel to connect the two ends of the helical path. In both types of ball screws, internal and external recirculation, the recirculating threaded component is most often the nut, but can also be the screw itself.

[0004] The capacity of a ball screw mechanism, which can be measured statically or dynamically by the load under which the mechanism remains functional without deteriorating, depends on various parameters, including the number and size of the active balls between the thread flanks of the screw and nut. The mechanism's efficiency, the ratio of energy delivered to energy supplied, depends on the friction within the mechanism. This friction is generated at the contact of the balls with the threads and at the contact of the active balls with each other in the loaded area between the thread flanks of the screw and nut, and to a lesser extent at the contact between the balls passing through the recirculation zones.

[0005] To increase capacity without increasing the number of recirculators in external recirculation mechanisms, the number of turns in the helical path of the balls between the screw and the nut can be increased, thereby increasing the number of balls in contact with the thread flanks of the screw and nut. However, the contact forces between the balls, which push against each other in the loaded zone, increase with the length of the helix in the loaded zone. This has a dual effect: it increases friction forces with the thread flanks and the risk of failure due to ball spalling. Furthermore, the number of balls simultaneously present in the recirculation channel increases proportionally. Thus, external recirculating ball screw mechanisms face a difficult compromise between capacity and efficiency.

[0006] In internal recirculating ball screw mechanisms, the number of balls not in simultaneous contact between the flanks of the two threads is low compared to the total number of balls, which is favorable to efficiency. However, the number of revolutions is limited to one per recirculator, thus limiting capacity. The solution to increase capacity is to increase the number of recirculators. But this increase requires increasing the volume and / or the number of recesses reserved for the recirculators in the recirculating threaded element, and distributing these recesses along the entire length of the recirculating threaded element. These constraints result in longer machining times, and sometimes even the impossibility of machining when the desired recess location is inaccessible. They also result in reduced axial compactness, as a significant portion of the recirculating threaded element's thread remains unused.

[0007] In certain applications, high precision is required in aligning the recirculating threaded element with the other threaded element. Starting with an internal recirculation mechanism, it is known to multiply the pairs of internal recirculators and distribute them along the length of the recirculating threaded element, each pair defining a closed internal recirculation circuit for one helix revolution. Similarly, starting with an external recirculation mechanism, it is tempting to use several pairs of external recirculators, distributed along the length of the recirculating threaded element, or to lengthen the helical path of the balls in an external recirculation mechanism by increasing the number of helix revolutions, with the drawbacks mentioned above.

[0008] The challenge then is to determine a means of recirculation combining the advantages of the two modes of recirculation, being efficient in terms of capacity, yield and axial alignment of the two threaded parts, while maintaining a great deal of freedom in positioning the recirculators and / or minimizing their number.

[0009] The invention aims to remedy the drawbacks of the prior art and to propose a threaded assembly allowing efficient recirculation combining the advantages of the two recirculation modes, easy to produce so as not to increase production costs and allowing satisfactory alignment of the associated threaded elements.

[0010] To this end, according to a first aspect of the invention, a threaded assembly comprising a recirculating threaded element of a ball screw mechanism is proposed, the recirculating threaded element comprising: a number C of helical bearing races centered on the same reference axis of the threaded assembly, having the same helix pitch P and open radially in the same radial reference direction of the recirculating threaded assembly, and a number N of housing cavities opening onto the helical bearing races and located axially at a distance from each other.The threaded assembly further comprises: at least one recirculation channel opening into two consecutive housing cavities from among the housing cavities, the two consecutive housing cavities opening onto a multi-turn raceway from among the helical raceways, the recirculation channel being positioned radially at a distance from the multi-turn raceway and set back from the multi-turn raceway, viewed in the radial reference direction. The threaded assembly further comprises: M deflectors, each deflector being housed in an associated housing cavity from among the N housing cavities, the deflectors forming recirculation paths, the recirculation paths including: at least two external recirculation paths, each opening onto the recirculation channel and the multi-turn helical raceway.Remarkably, the recirculation paths also include at least one internal recirculation path turned in the radial reference direction and opening onto the same internal recirculation loop of an internal running track among the running tracks.

[0011] The threaded assembly allows for two distinct and independent types of recirculation on a single recirculating threaded component with a helical bearing surface. In this way, the threaded assembly offers the advantages of both internal and external recirculation.

[0012] Preferably, M N in the context where a cavity is intended to house at most one deflector. If a cavity is large enough to accommodate multiple deflectors, this inequality is obviously no longer relevant. In the preceding definition, the numbers C, M, and N are integers greater than or equal to 1. M=1, in particular, when at least a portion of the recirculation channel and the two deflectors, each located at one end of the recirculation channel, are made of a single piece forming a single deflector.

[0013] According to one embodiment, M 2. Thus, the recirculation channel does not need to be partially formed by the deflector, unlike when M=1. It is therefore unnecessary to machine the threaded recirculating element along the recirculation channel so that it opens radially to the outside, which can be advantageous if the element has characteristics that do not allow for this type of machining. It is also easier to position and space two separate recirculation paths when they are located on two separate deflectors.

[0014] Each recirculation path consists of concave walls of one of the recirculation deflectors, walls which define a recirculation trajectory for the balls of the ball screw mechanism. The term trajectory, here and elsewhere in the text, is the imaginary line defined by the successive loci of the centers of curvature of the concave walls, viewed in successive cross-sectional planes in which the radius of curvature of the walls is smallest. Since the balls of the ball screw mechanism have a ball radius very close to, and slightly smaller than, the smallest radius of curvature observed at the walls, the trajectory is very close to the trajectory of the centers of the balls circulating in the recirculation paths.

[0015] In one embodiment, the internal recirculation path describes an S-shaped internal trajectory with two internal ends opening onto the internal running track in opposite directions. The internal recirculation path is formed by recirculation deflector walls which, in one embodiment, form an open profile when viewed in any cross-sectional plane perpendicular to the internal trajectory defined by the internal recirculation path.

[0016] In one embodiment, the recirculation paths include at least one additional internal recirculation path. Adding an additional internal recirculation path allows the load to be distributed over a larger number of balls without significantly reducing efficiency. Preferably, the external recirculation path is located axially between the internal recirculation path and the additional internal recirculation path. This provides a balance and symmetry that are favorable for bidirectional operation under load. Preferably, the internal raceway and the additional internal raceway have the same coil diameter. This contributes to the overall symmetry and simplifies the sizing of the components involved in the internal recirculations.

[0017] Where appropriate, the threaded assembly may be provided to have at least one additional recirculation channel opening into two additional consecutive housing cavities among the housing cavities, the two additional consecutive housing cavities opening onto an additional multi-turn raceway among the helical raceways, the additional recirculation channel being positioned radially away from the additional multi-turn raceway, set back from the additional multi-turn raceway, viewed in the radial reference direction, the recirculation paths including: at least two additional external recirculation paths each opening onto the additional recirculation channel and the additional multi-turn helical raceway.In this scenario, the multi-turn raceway and the additional multi-turn raceway are assumed to have the same turn diameter and / or the same number of turns. Increasing the number of additional channels significantly increases the load capacity of the ball screw mechanism, but at the cost of a significant decrease in efficiency.

[0018] In one embodiment, the multi-turn raceway and the internal raceway have the same turn diameter. This allows the multi-turn raceway, the internal raceway, and, if applicable, the additional internal raceway, to be manufactured with a single thread for the recirculating threaded element. In this scenario, the recirculating threaded element can advantageously be a single piece. It should also be noted that identical sized balls can then be used to circulate on the multi-turn raceway, the internal raceway, and, if applicable, the additional internal raceway, thus simplifying assembly and maintenance.

[0019] In another embodiment, the multi-turn raceway has a turn diameter greater than the turn diameter of the internal raceway. Alternatively, the multi-turn raceway has a turn diameter smaller than the turn diameter of the internal raceway. The recirculating threaded element can then advantageously be manufactured in several parts, although manufacturing it in one piece is also possible. The choice of different turn diameters for the multi-turn raceway and the internal recirculating raceway allows for the provision of different mechanism sections with varying radial dimensions, for example, to adapt to the space constraints of a particular application.In the case of a larger coil diameter for the internal recirculation path, it will also be possible to accommodate a greater number of balls on the internal recirculation path, the number of balls on the multi-coil recirculation path always being limited by the friction specific to external recirculation, as discussed above regarding the prior art.

[0020] It is advantageous to minimize the number of housing cavities to limit machining operations on the recirculating threaded component and / or the assembly of the deflectors. To achieve this, at least one deflector can be a multi-deflector, with the multi-deflector forming at least two of the recirculation paths housed within a single multi-cavity.

[0021] In particular, at least one internal and one external recirculation path can be provided among the recirculation paths. The multi-cavity housing for the multi-deflector is then formed so as to open at one end of the multi-turn bearing raceway and at one end of the internal bearing raceway, which in this scenario are adjacent to each other and formed on a single thread of the recirculating element. This results in a particularly compact assembly in the axial direction.

[0022] Assuming two multi-turn rolling paths are provided, separated by an internal rolling path, at least one internal recirculation path and two external recirculation paths can be considered among the recirculation paths, one of the two external recirculation paths opening into the recirculation channel, the other of the two external recirculation paths opening into another external recirculation channel at least partially formed in the recirculating threaded element.

[0023] Other configurations of multiple deflectors are envisaged, including a multiple deflector with at least two internal recirculation paths among the recirculation paths or with at least two external recirculation paths among the recirculation paths.

[0024] In applications where a particularly precise relative alignment between the screw and the nut is required, it is advantageous to distance the internal raceway from the multi-turn raceway. Thus, according to various embodiments: the internal raceway is located axially at a distance from the multi-turn raceway greater than twice the helix pitch P, and preferably greater than five times the helix pitch P; the internal recirculation path is formed on an internal deflector among the deflectors, and the two external recirculation paths are formed on one or two external deflectors among the deflectors, distinct from the internal deflector.

[0025] These configurations will be particularly favorable to embodiments with a different coil diameter for the internal raceway and the multi-coil raceway.

[0026] According to one embodiment, the internal raceway is located axially at a distance from the multi-turn raceway less than 2 times the helix pitch P and / or the internal recirculation path is formed on a multi-baffle among the baffles, which also forms one of the two external recirculation paths.

[0027] Assuming the threaded assembly also includes an additional internal recirculation path, analogous considerations lead to configurations in which: the additional internal rolling path is located axially at a distance from the multi-turn rolling path greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P; and / or the additional internal recirculation path is formed on an additional internal deflector among the deflectors, and the two external recirculation paths are formed on one or two external deflectors among the deflectors, distinct from the additional internal deflector; and / or the additional internal rolling path is located axially at a distance from the internal rolling path greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P;and / or an additional internal recirculation path is formed on an additional internal baffle among the baffles, and the internal recirculation path is formed on an internal baffle among the baffles, distinct from the additional internal baffle.;

[0028] In configurations where compactness is prioritized, the internal raceway can be brought closer to the multi-turn raceway. Thus, according to one embodiment, the additional internal raceway is located axially at a distance from the multi-turn raceway less than twice the helix pitch P. Preferably, the additional internal recirculation path is formed on an additional mixed deflector among the deflectors, which also forms one of the two external recirculation paths.

[0029] Following a particularly advantageous embodiment, each of the deflectors is made in a single piece.

[0030] In one embodiment, at least one deflector comprises a functional positioning zone, the functional positioning zone comprising at least one positioning shoulder, preferably two positioning shoulders, oriented radially in the radial reference direction. Preferably, the housing cavity associated with the deflector comprising a functional positioning zone includes a zone complementary to the functional positioning zone of the deflector. Even more preferably, the complementary zone comprises one or more bearing surfaces against which the shoulder(s) of the recirculation deflector bear. The functional positioning zone may have specific shapes to facilitate the insertion and correct positioning of the recirculation deflector in the housing cavity.Preferably, the recirculation deflector includes keying features to prevent incorrect insertion into the housing cavity. If necessary, the recirculation deflector may be fitted with an elastic hook or other device to secure it in the housing cavity.

[0031] To facilitate the manufacture of deflectors dedicated to external recirculation, in particular by molding or by machining, it is provided that the external recirculation paths describe an external trajectory with two external ends, at least one of the external recirculation paths is made up of walls of the recirculation deflector which, seen in any cutting plane perpendicular to the external trajectory, form an open profile.

[0032] In one embodiment, the recirculating threaded element is a nut, with the radial thread direction facing the helix axis. The nut may then have one or more flanges and / or collars on its outer surface, the recirculation channel(s) allowing the balls to recirculate while avoiding machining the raceway from this outer surface. For example, the nut has a flange located axially between two consecutive housing cavities and projecting radially in the opposite direction to the radial thread direction relative to the two consecutive housing cavities.

[0033] According to another aspect of the invention, it relates to a ball screw mechanism comprising: a recirculating threaded element, a complementary threaded element, having a complementary helical raceway rotated radially towards the helical raceway of the recirculating threaded element, and external recirculating balls housed in a closed volume delimited at least partially by the helical raceway, the complementary helical raceway, the recirculation channel and the external recirculation path, notable in that the recirculating threaded element is a recirculating threaded element as described above, the ball screw mechanism further comprising internal recirculating balls housed in a closed volume delimited at least partially by the helical raceway,the complementary helical raceway and the internal recirculation path and external recirculation balls housed in a closed volume delimited at least partially by the helical raceway, the complementary helical raceway, the two external recirculation paths and the recirculation channel.

[0034] In one embodiment, the external recirculation balls and the internal recirculation balls have identical diameters and / or are made of the same material. The balls are then interchangeable.

[0035] Alternatively, to optimize each type of ball according to the loads to which it is subjected, it can be provided that the external recirculation balls and the internal recirculation balls have a different diameter and / or are made of a different material. BRIEF DESCRIPTION OF THE FIGURES

[0036] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures.

[0037] Laillustre, in an axial cross-sectional view, an assembly according to a first embodiment, the assembly comprising a nut and two recirculation deflectors.

[0038] Laillustre an axial cross-sectional view of a mechanism comprising the assembly according to the first embodiment, a screw and balls.

[0039] Laillustre another view of the mechanism comprising the assembly according to the first embodiment, and a screw.

[0040] Laillustre, in an isometric view, the recirculation deflector of the first embodiment.

[0041] Laillustre a view in a cross-section of the mechanism comprising the assembly according to the first embodiment, and a screw.

[0042] Laillustrate a view in a cross-section along an internal recirculation trajectory of the mechanism.

[0043] Laillustre en perspective un dispositif compris un ensemble selon une première variant de l’un embodiment, le ensemble compris un vise et des deflecteurs decirculation, et un noix part coupé coupé.

[0044] Laillustre en une vue isométrique, le deflecteur de recirculer de la première variant de la premier embodiment.

[0045] Laillustre, in a longitudinal sectional view, the mechanism comprising the assembly according to the first variant of the first embodiment and a nut.

[0046] The schematic illustration shows the assembly comprising a screw and four deflectors, one of which is a hybrid.

[0047] The schematic illustration shows the assembly comprising a screw, four deflectors including a triple one presenting three distinct recirculation paths.

[0048] The diagram schematically illustrates the assembly comprising a nut and four deflectors, two of which are hybrid.

[0049] The diagram schematically illustrates the assembly according to a second variant of the first embodiment, comprising a screw, two recirculation channels and five deflectors, including two double hybrids and one triple hybrid.

[0050] The diagram schematically illustrates the assembly according to the second variant of the first embodiment, comprising a nut, two recirculation channels and five deflectors, including two double hybrids and one triple hybrid.

[0051] Laillustre, in a cross-sectional view, an assembly according to a second embodiment, the assembly comprising a nut and three recirculation deflectors.

[0052] Laillustre, in an isometric view, the assembly according to the second embodiment, the assembly comprising a nut and four recirculation deflectors and a screw.

[0053] The illustration shows the assembly according to the first embodiment in which the assembly includes a nut with variable helix radius and variable thread flank curvature radius and three recirculation deflectors.

[0054] The assembly is illustrated according to the second embodiment in which the assembly includes a screw with variable helix radius and variable thread flank curvature radius and three recirculation deflectors.

[0055] The diagram schematically illustrates the assembly according to a first variant of the first embodiment, comprising a nut with variable helix radius and an additional recirculation path.

[0056] The diagram schematically illustrates the assembly comprising a screw with a variable helix radius and thread according to the second embodiment.

[0057] The diagram schematically illustrates the assembly comprising a nut with a variable helix radius and thread according to the second embodiment.

[0058] For clarity, identical or similar elements are identified by identical reference symbols across all figures. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0059] Figures 1 to 6 illustrate a ball screw mechanism 10 comprising two threaded members, namely a nut 12 and a screw 14 aligned on a common reference axis 100, and balls 16A, 16B (Figure 2) disposed between a thread 18 of the nut 12 and a thread 20 of the screw 14, to guide the relative helical motion between the nut 12 and the screw 14. Each thread 18, 20 has a helical groove forming a number C of helical raceways, with C and comprising at least one internal raceway 18A and one multi-turn raceway 18B, both helical. The respective flanks of the helical raceways form a helical thread 26,72 of pitch P, following a profile that is constant in any cutting plane perpendicular to the helical thread. In this first embodiment, C=3. Each of the helical raceways has a mean radius extending radially between the common reference axis 100 and the center of a mean radius of curvature of the flanks of the helical groove of said helical raceway. In addition, the nut 12 has an external annular surface 60 having a working area 62. The working area 62 may include a structural element and / or a coating that cannot be machined, such as a collar or a flange 64.

[0060] One of the two threaded elements, in this embodiment the nut 12, will be referred to hereafter as the recirculation threaded element 13, because it is equipped with two recirculation deflectors 22 and a recirculation channel 32, the other threaded element, here the screw 14, being designated as the complementary threaded element 15. The recirculating threaded element 13 generally comprises a number 1 of recirculation channels (here, B=1). The recirculating threaded element 13 and the associated recirculating deflectors 22 form a threaded assembly 70. Each of the recirculating deflectors 22 can be made of light metal or, preferably, of plastic. Each of the recirculating deflectors 22 is housed in a housing cavity 24 formed in the recirculating threaded element 13, and which passes through a thread 26 of the thread 18 of the recirculating threaded element 13, to open onto two areas 28 of the thread groove 18 on either side of the thread 26. The housing cavities 24 are here oriented radially and are through holes, but can be blind holes, mortises for example. Each housing cavity 24 has lateral walls preferably parallel to a radial direction of the housing cavity 24, and two junction areas with the two areas 28 of the thread groove 18.The housing cavities24 may also have keying features, i.e. shapes or devices which ensure that the recirculation deflector22 can only be inserted correctly, thus avoiding assembly errors.

[0061] The threaded assembly 70 generally comprises N housing cavities 24 and M recirculation deflectors 22, with M N. In this embodiment, there are two housing cavities 24 and recirculation deflectors 22 (M=N=2), and each recirculation deflector 22 has a reference axis 200, which, after mounting in the associated housing cavity 24, is intended to coincide with the helix axis 100 of the thread 18 of the recirculation threaded element 13. Each recirculation deflector 22 has a radial reference direction 300, which, after mounting in the associated housing cavity 24, is intended to be oriented in the same direction as the thread 18 of the recirculation threaded element 13, therefore, in this embodiment, towards the reference axis 200 and the helix axis 100. The threaded assembly 70 also includes a number Q of recirculation deflectors comprising at least one external recirculation path 36, with Q B, preferably Q B+1 (here, Q=2). Q can be equal to B in particular when at least a portion of the recirculation channel and the two deflectors located respectively at one and the other end of the recirculation channel are made of a single piece, forming a single deflector.

[0062] In addition, each recirculation deflector22 presents a generally rectangular functional recirculation zone30 in which at least two distinct and disjoint recirculation paths34,36 are defined and, more specifically, at least one internal recirculation path34 and one external recirculation path36, so that each recirculation deflector22 can be described as a multiple deflector (in the sense that it presents several recirculation paths) and as a mixed deflector, also called a hybrid, in the sense that it presents at least one internal recirculation path and at least one external recirculation path.

[0063] For each point on the wall of the internal recirculation path 34, it is possible to define a cross-sectional plane passing through said point and perpendicular to the wall, in which the wall is concave and has a minimum radius of curvature. An internal recirculation path T1 can then be defined step by step. This path is a line formed by the successive centers of curvature with the smallest radius of the internal recirculation path 34. This line also represents the successive passage points of the centers of the balls rolling on the walls of the internal recirculation path. This internal path T1 has an S-shape, with two internal extremities 40 and 140 connected by an intermediate portion 42 comprising two curved transition zones 43 separated by a median zone 38. The two internal extremities 40 and 140 are located radially at the same distance D1 from the reference axis 100 and axially at a distance L1 from each other.The intermediate portion 42 is located radially inset from the two internal ends 40, 140, viewed in the radial reference direction 300, that is to say that the intermediate portion 42 is located at least partially at a distance D2 from the reference axis 100, which is greater than D1, as illustrated in particular in figures 3 and 6. The internal recirculation path has a bottom 50 radially closer to the thread 26 of the threaded element at the internal ends 40, 140 than at any other level. The bottom 50 is tangent to a bottom 44 of the net 26 at the internal ends 40, 140. The bottom 50 and the bottom 44 of the net 26 are, at the internal ends 40, 140, radially at the same distance from the net 26. The internal recirculation path 34 presents, in any plane perpendicular to the internal recirculation trajectory T1 in S, a concave profile with a radius of curvature greater at every point than a predetermined radius R0, such that. , And . The two internal ends40,140 of the internal trajectoryT1 open into the thread groove18 of the recirculating threaded member13, preferably at a point located on a pitch line of the thread groove18 of the recirculating threaded member13. The portion of the thread groove 18 located between the two internal ends 40, 140 defines an internal raceway 18A, on less than one turn of the thread 18, for internally recirculating balls 16A, which circulate in a closed loop in a volume delimited by the internal raceway 18A, the internal recirculation raceway 34 and the thread groove 20 of the complementary threaded element 15 constituted here by the screw 14. The two internal ends 40, 140 of the internal trajectory T1 are located on the same helix of radius D1 and constant pitch equal to the pitch P of the recirculating threaded element 12 and centered on the reference axis 100, and are oriented in opposite angular directions.

[0064] The external recirculation path 36 has at least one portion oriented in the centripetal reference direction 300 and another portion oriented in a direction parallel to the recirculation channel 32, itself parallel to the reference axis 100. The external recirculation path 36 describes an external path T2, which is a line formed by the successive centers of curvature of smallest radius of the external recirculation path 36. This external path T2 has an L-shape with a first external guide end 46 and a second external guide end 48, between which extends a transitional portion 51. The first external guide end 46 is located at the same distance D1 from the reference axis 100 as the two internal guide ends 40, 140, the second 48 of the two ends of the external recirculation path 36 being located radially recessed with respect to the first 46 external end, viewed in the radial reference direction 300.More specifically, the two external ends46, 48 are located radially at a distance H from each other, such that. The external recirculation path 36 has a bottom 52 which forms, at the first external guide end 46, a scoop projecting from a bottom of the thread 18, in the radial reference direction 300, then, from the first external guide end 46 to the second external guide end 48, moves radially away continuously from the thread 26 of the thread 18 of the recirculating threaded element 13. The first external guide end 46 is located on the same helix of radius D1 and constant pitch equal to the pitch P of the recirculating threaded element 12 and centered on the reference axis 100, as the two internal guide ends 40, 140.

[0065] Preferably, the first external guide end 46 and the second internal end 140 open in opposite directions onto the same helix turn of radius D1 and constant pitch centered on the reference axis 100. The first external guide end 46 and the first internal end 40 are adjacent, separated axially by a distance equal to the pitch P, and by one helix turn from each other.

[0066] Each recirculation deflector 22 further comprises a positioning base 54 opposite the recirculation functional zone 30. The positioning base 54 is connected to the recirculation functional zone 30 by a connecting functional zone 56. The positioning base 54 and / or the connecting functional zone 56 may have shoulders 58 and / or positioning shapes, flats or elastic tabs for example, forming counterforms of the housing cavity 24 and its locating features in which the positioning base 54 and / or the connecting functional zone 56 are intended to be housed. The shoulders 58 are preferably formed when the recirculation deflector 22 is intended to be inserted into the nut 12, as illustrated in the figure.

[0067] Each recirculation deflector22 can be made in one piece, for example by additive manufacturing, or preferably by molding, because it has few undercuts.

[0068] An assembly 70 is formed when the mixed recirculation deflectors 22 are in the operating position, i.e., housed in the associated housing cavities 24 of the recirculating threaded element 13. The axial offset between the two internal ends 40, 140 of the internal recirculation path 34 allows the balls to pass through the thread 26 of the thread 18, as illustrated in Figure 3, radially bypassing a thread 72 of the thread 20, and thus achieving internal recirculation on one turn of the helix of the thread 18. The radial offset between the first external guide end 46 and the second external guide end 48 allows the thread 18 and the recirculation channel 32 to be continuously linked, as illustrated in Figures 3 to 5, the recirculation channel 32 being tangent to the first external guide end 46 and the thread 18 being tangent to the second external guide end 48.Finally, the axial offset between the second external guide ends48 of the two recirculation deflectors22 opening onto the recirculation channel32 allows a connection between the two axial ends of the recirculation channel32 and a portion of the thread groove18 of the recirculating threaded element13 which has several turns, preferably more than two turns, for example five turns or more, this portion being designated as a multi-turn bearing raceway or external bearing raceway18B.

[0069] In this embodiment, each mixed recirculation deflector 22 allows the recirculation of the balls 16A, 16B in two simultaneous but distinct ways: a part of the balls 16A is recirculated in an internal recirculation circuit, composed of the internal rolling track 18A on less than one turn of the helix of the thread 18, and the internal recirculation track 34; and another part of the balls 16B is recirculated in an external recirculation circuit, composed of the multi-turn rolling track 18B (in this embodiment, four turns), the recirculation channel 32 and the two external recirculation tracks 36 reformed in the two recirculation deflectors 22.

[0070] Thus, the ball screw mechanism10 comprising two mixed recirculation deflectors22 has two internal recirculation circuits positioned axially on either side of an external recirculation circuit, directly adjacent to the latter.

[0071] The invention is particularly useful when the recirculating threaded element 13 is considered large, i.e., when the number of turns and / or the geometric dimensions are substantial, for example, when the recirculating threaded element 13 comprises X turns with X such that X ≥ 7, preferably X ≥ 9, preferably even more so X ≥ 12, and / or has a length greater than 15 cm. Such a large recirculating threaded element 13 introduces uncertainty in the axial positioning of the complementary threaded element 15 relative to the threaded assembly 70. The external recirculation path 36 is then located less than 5 turns, preferably less than 2 turns, from at least one of the two ends of the bearing path of the recirculating threaded element 13. In this way, the internal raceways18A, together with the multi-turn raceways18B, maintain the coaxial alignment of the recirculating threaded element13 and the complementary threaded element15.

[0072] All the balls 16A of the internal recirculation circuit are in continuous contact with the two threaded members of the mechanism, or with one of the two threaded members and the internal recirculation path 34, and all are active, in the sense that they can transmit a load between the two threaded members, except for those located on the internal recirculation path 34. The internal recirculation circuit, which has only slightly less than one helix turn between the two inner ends, makes it possible to substantially increase the load, but with a small increase in friction. During operation, the ball 16B of the external recirculation circuit subjected to the greatest stress is the one which, in the direction of rotation, pushes the other balls to one of the end turns in the immediate vicinity of one of the outer ends 46 due to the axial stresses exerted on said mechanism 10.It is therefore advantageous to have internal recirculation circuits at both ends of the threaded parts12,14 since they allow for the implementation of a recirculation comprising proportionally more balls than external recirculation, giving it a better efficiency, and thus helping to support a greater load.

[0073] Such a ball screw mechanism 10 thus allows, via the external recirculation circuit, a nut 12 with an unmachined outer annular surface 60 in the working area 62. In this way, the coating or element of the outer annular face 60 of the nut 12 is not damaged. Furthermore, the two internal recirculation circuits located at the two ends of the threaded recirculating member 13, which have increased resistance to the stresses to which the balls of these internal recirculation circuits are subjected, support the external recirculation circuit.

[0074] According to a first variant of the first embodiment illustrated in figures 7 to 13 and 20, the recirculating threaded member 13 is the screw 14. The radial reference direction 300 is then opposite to that of the previous embodiment and the recirculation channel 32 is in the body of the screw 14.

[0075] According to an unillustrated variant, the mechanism 10 may have only one mixed recirculation deflector 22. In this variant, the mechanism must include another recirculator with only the function of an external recirculator (known in the prior art), so that the external recirculation circuit initiated by the recirculation deflector 22 is closed. This variant can be used, in particular, if it is necessary to further reduce the axial dimensions of the mechanism 10, as this variant allows for the elimination of one turn.

[0076] According to a second variant of the first embodiment, illustrated in Figures 13 and 14, the recirculation deflector 22 can be triple, that is, have three distinct recirculation paths. For example, the triple mixed recirculation deflector 22 can have two successive internal recirculation paths and one external recirculation path. Also, if the mechanism 10 has an additional recirculation channel 32', and more particularly located substantially near the recirculation channel 32, the triple recirculation deflector 22 can have an internal recirculation path between two external recirculation paths, each external recirculation path being connected to one of the two recirculation channels.

[0077] Of course, variations of these mixed recirculators can be implemented with a predetermined number of internal recirculation paths between the two external recirculation paths. In other words, a mixed recirculator can include at most two external recirculation paths and any number of internal recirculation paths, provided that each external recirculation path has only one adjacent internal recirculation path.

[0078] According to a second embodiment, illustrated in Figures 15 to 21, the mechanism 10 has only simple deflectors, that is, deflectors each having only one recirculation path. In this second embodiment, the threaded assembly 70 has two helical raceways (C=2), one of which is a multi-turn raceway 18B and the other an internal raceway 18A. The threaded assembly 70 then has the housing cavities 24, and there are three recirculation deflectors 22 (M=N=3). The internal recirculation path is formed on one of the recirculation deflectors 22, called the internal deflector. An external recirculation path is formed on one of the recirculation deflectors 22, called the external deflector.

[0079] According to a first variant of the second embodiment, illustrated in Figures 19 to 21, the threaded assembly 70 further comprises at least one additional internal recirculation path 34', preferably identical to the internal recirculation path 34. The threaded assembly 70 then comprises four recirculation paths and three helical bearing paths (C=3). The additional internal recirculation path 34' is then positioned at a distance Dx greater than 2 pitchesP, preferably greater than 5 pitchesP, from one of the two ends of the threaded assembly 70, more particularly at the end of the helical section of the recirculating threaded element 13. Preferably, the additional internal recirculation path 34' is positioned axially opposite the internal recirculation path 34.Thus, the ball screw mechanism 10, comprising four recirculation deflectors 22, has two internal recirculation circuits positioned axially on either side of an external recirculation circuit. In this way, the additional internal recirculation path 34' ensures the alignment of the complementary threaded element 15 on the same reference axis as the threaded assembly 70. Moreover, generally, during operation, the end turn of the recirculating threaded element 13 subjected to the greatest stress is due to the axial stresses exerted on the mechanism 10. It is therefore advantageous to have internal recirculation paths 34, 34' at both ends of the threaded elements 12, 14 since they allow for recirculation with a proportionally larger number of balls than external recirculation, thus providing better efficiency and contributing to supporting a greater load.

[0080] According to a second variant of the second embodiment illustrated in Figures 13 and 14, B=2, the recirculating threaded element 13 includes an additional recirculation channel 32'. The threaded assembly 70 then includes at least one additional external recirculation path 36. This additional external recirculation path 36 can be integrated into the threaded assembly 70 by adding an additional recirculation deflector 22 or by using a hybrid recirculation deflector 22 comprising: at least two external recirculation paths from among the recirculation paths, and is then called a double deflector; or at least one internal recirculation path and two external recirculation paths from among the recirculation paths, preferably with the internal recirculation path positioned between the two external recirculation paths, and is then called a triple hybrid deflector.

[0081] Each deflector generally has dimensions that depend on the radius and pitch of the helix as well as the radius of curvature of the flanks of the thread with which the recirculation paths of said deflector must cooperate.

[0082] For example, according to a third embodiment illustrated in Figures 17 to 21, any one of the two threaded members has a first portion of helical raceway mean radius R1 and a second portion of helical raceway mean radius R2, with R1 R2. This characteristic may be desirable to reduce the volume and / or quantity of material in at least a portion of the recirculating threaded element 13 and / or the complementary threaded element 15. A single mechanism 10 with a variable helix radius may have two hybrid double recirculators, each with an internal recirculation path and an external recirculation path, designed to terminate in distinct helical bearing races of different dimensions, each located on a portion of the thread with a different helix radius. Naturally, depending on the sequence of portions with different helix radii, the ball screw mechanism 10 may require that at least one of the two threaded elements be composed of at least two parts. For example, the nut may be formed of two parts, such a nut being designed to be mounted with the screw interposed between the two parts forming the nut during assembly.

[0083] In summary, as illustrated in Figures 8 to 15, the ball screw mechanism 10 comprises the threaded assembly 70, the threaded assembly 70 including the recirculating threaded element 13 and the recirculation paths. The recirculating threaded element 13 can be the screw or the nut, and can also have variable thread dimensions, meaning that the helix radius varies axially (as illustrated in Figures 17 to 21) and / or that the radii of curvature of the flanks of the helical groove are variable (as illustrated in Figure 1). Consequently, two balls from two different recirculation paths can have different radii.The recirculation paths of the threaded assembly 70 are defined by deflectors, each of these deflectors being able to present: at least one internal recirculation path 34; and / or at least two internal recirculation paths 34; and / or at least one external recirculation path 36; and / or at least one external recirculation path 36 and one internal recirculation path 34; and / or at least two external recirculation paths 36 and one internal recirculation path 34; and / or at least one external recirculation path 36 and two internal recirculation paths 34.

[0084] Double or triple and / or hybrid deflectors are preferred, since they allow the recirculation functions of two or three distinct recirculation paths to be shared on the same recirculation deflector22, resulting in increased compactness, a reduction in the number of parts to be produced, and simplified assembly of a ball screw mechanism10 incorporating this type of recirculation deflector22. This sharing, for example of two recirculation functions of two distinct recirculation paths on the same deflector, is made possible when the first external guide end46 and the second internal end140 open onto the same helix turn with a radius identical to the average radius of the helical raceway and a constant pitch centered on the reference axis100.The first external guide end46 and the first internal end40 are therefore juxtaposed, separated by a distance less than the width of the thread26, and open onto the two distinct turns of the helix.

[0085] Furthermore, for the sake of stability and to ensure the coaxial positioning of the threaded element 13 and the complementary threaded element 15, it is preferable that the internal bearing race 18A be located axially at a distance from the multi-turn bearing race 18B greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P; or that the internal bearing race 18A be located axially at a distance from the multi-turn bearing race 18B less than 2 times the helix pitch P; and / or that the additional internal bearing race 18A be located axially at a distance from the multi-turn bearing race 18B greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P; or that additional internal raceway 18A is located axially at a distance from the multi-turn raceway 18B less than 2 times the helix pitch P;and / or that additional internal raceway 18A is located axially at a distance from the internal raceway 18A greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P.;

[0086] Naturally, the examples shown in the figures and discussed above are given for illustrative purposes only and are not exhaustive. It is explicitly intended that the different embodiments illustrated can be combined to create other solutions.

Claims

Threaded assembly comprising a recirculating threaded element (13) of a ball screw mechanism (10), the recirculating threaded element (13) comprising: a number C of helical bearing races centered on the same reference axis of the threaded assembly, having the same helix pitch P and open radially in the same radial reference direction (300) of the recirculating threaded assembly, a number N of housing cavities (24) opening onto the helical bearing races and located axially apart from each other, the threaded assembly further comprising: at least one recirculation channel (32) opening into two consecutive housing cavities (24) among the housing cavities (24), the two consecutive housing cavities opening onto a multi-turn bearing race (18B) among the helical bearing races,the recirculation channel (32) being positioned radially at a distance from the multi-turn raceway (18B) and set back from the multi-turn raceway (18B), viewed in the radial reference direction (300), a number M of deflectors, each of the deflectors being housed in a housing cavity (24) associated among the N housing cavities (24), the deflectors forming recirculation paths, the recirculation paths including: at least two external recirculation paths (36) each opening onto the recirculation channel (32) and the helical multi-turn raceway (18B), characterized in that the recirculation paths further include at least one internal recirculation path (34) rotated in the radial reference direction (300) and opening onto the same internal recirculation turn of an internal raceway (18A) among the raceways. Threaded assembly according to claim 1, characterized in that the recirculation paths include at least one additional internal recirculation path (34'). Threaded assembly according to claim 2, characterized in that the external recirculation path is located axially between the internal recirculation path and the additional internal recirculation path. Threaded assembly according to any one of claims 2 to 3, characterized in that the internal raceway (18A) and the additional internal raceway (18A) have the same turn diameter. Threaded assembly according to any one of the preceding claims, characterized in that: the multi-turn raceway (18B) and the internal raceway (18A) have the same turn diameter; or the multi-turn raceway (18B) has a turn diameter greater than a turn diameter of the internal raceway (18A); or the multi-turn raceway (18B) has a turn diameter less than a turn diameter of the internal raceway (18A). Threaded assembly according to any one of the preceding claims, characterized in that at least one deflector is a multiple deflector, the multiple deflector forming at least two of the recirculation paths, preferably: at least one internal recirculation path and one external recirculation path among the recirculation paths; or at least one internal recirculation path and two external recirculation paths among the recirculation paths, one of the two external recirculation paths opening into the recirculation channel, the other of the two external recirculation paths opening into another external recirculation channel at least partially formed in the threaded recirculating member; or at least two internal recirculation paths among the recirculation paths; or at least two external recirculation paths among the recirculation paths. Threaded assembly according to any one of the preceding claims, characterized in that: the internal raceway (18A) is located axially at a distance from the multi-turn raceway (18B) greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P and / or the internal recirculation path is formed on an internal deflector among the deflectors, and the two external recirculation paths are formed on one or two external deflectors among the deflectors, distinct from the internal deflector. Threaded assembly according to any one of claims 1 to 6, characterized in that: the internal raceway (18A) is located axially at a distance from the multi-turn raceway (18B) less than 2 times the helix pitch P and / or the internal recirculation path is formed on a multi-baffle among the baffles, which also forms one of the two external recirculation paths. Threaded assembly according to any one of claims 7 to 8 in combination with any one of claims 2 to 4, characterized in that: the additional internal raceway (18A) is located axially at a distance from the multi-turn raceway (18B) greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P and / or the additional internal recirculation raceway is formed on an additional internal deflector among the deflectors, and the two external recirculation raceways are formed on one or two external deflectors among the deflectors, distinct from the additional internal deflector; and / or the additional internal raceway (18A) is located axially at a distance from the internal raceway (18A) greater than 2 times the helix pitch P, and preferably greater than 5 times the helix pitch P;and / or an additional internal recirculation path is formed on an additional internal baffle among the baffles, and the internal recirculation path is formed on an internal baffle among the baffles, distinct from the additional internal baffle.; Threaded assembly according to any one of claims 7 to 8 in combination with any one of claims 2 to 4, characterized in that: the additional internal raceway (18A) is located axially at a distance from the multi-turn raceway (18B) less than 2 times the helix pitch P and / or the additional internal recirculation path is formed on an additional mixed deflector among the deflectors, which also forms one of the two external recirculation paths. Threaded assembly according to any one of the preceding claims, characterized in that each of the deflectors is made in one piece. Threaded assembly according to any one of the preceding claims, characterized in that the external recirculation paths (36) describe an external trajectory (T2) with two external ends (46,48), at least one of the external recirculation paths is constituted by walls of the recirculation deflector which, seen in any cutting plane perpendicular to the external trajectory (T2), form an open profile. Threaded assembly according to any one of the preceding claims, characterized in that the recirculating threaded element is a nut, the radial direction of the thread being turned towards the helix axis. Threaded assembly according to claim 13, characterized in that the nut comprises a flange located axially between two consecutive housing cavities, and projecting radially opposite to the radial direction of the thread relative to the two consecutive housing cavities. Ball screw mechanism (10) characterized in that it comprises a recirculating threaded element (13), a complementary threaded element (15), having a complementary helical raceway radially oriented towards the helical raceway of the recirculating threaded element, external recirculating balls housed in a closed volume delimited at least partially by the helical raceway, the complementary helical raceway, the recirculation channel and the external recirculation path, characterized in that the recirculating threaded element is a recirculating threaded element according to any one of claims 1 to 14, the ball screw mechanism further comprising internal recirculating balls housed in a closed volume delimited at least partially by the helical raceway,the complementary helical raceway and the internal recirculation path and external recirculation balls housed in a closed volume delimited at least partially by the helical raceway, the complementary helical raceway, the two external recirculation paths and the recirculation channel. Ball screw mechanism according to claim 15, characterized in that the external recirculation balls and the internal recirculation balls have identical diameters and / or are made of the same material. Ball screw mechanism according to claim 15, characterized in that the external recirculation balls and the internal recirculation balls have a different diameter and / or are made of a different material.

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