Ball screw device

Abstract

To provide a ball screw device for suppressing a positional displacement of tips of leg parts.SOLUTION: A ball screw device comprises a screw shaft, a nut, balls, a circulation component and a fixing component. Two penetration holes penetrating in an assembling direction, and long in a cross direction are formed at the nut. The two penetration holes are formed while being split to one and the other in the cross direction with a virtual line as a boundary. The circulation component has a main body part fixed to the fixing component, two leg parts inserted into the penetration holes, and two bent parts for connecting the main body part and the leg parts. An internal peripheral face of each of the penetration holes has a pair of opposing faces which oppose each other in the cross direction. A pair of the opposing faces has a first opposing face which is arranged while being shifted to a virtual line, and a second opposing face which is arranged separately from the virtual line. The leg parts are inclined so as to approach a side of the second opposing face from the first opposing face as progressing toward tips of the let parts. The first opposing face presses the leg parts. The tips of the leg parts are pressed to the second opposing face.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a ball screw device. [Background technology]

[0002] A ball screw device is a device that converts rotary motion into linear motion or linear motion into rotary motion. The ball screw device includes a screw shaft, a nut, a plurality of balls that roll on a track between the screw shaft and the nut, and a circulating part that returns the balls that have rolled from one end of the track to the other end of the track.

[0003] One example of a circulation component is a tubular component as shown in Patent Document 1. This tubular circulation component includes a main body extending along the outer circumferential surface of the nut, a bent portion bent from the main body, and legs extending from the bent portion. The legs are inserted into through holes that penetrate the inner and outer circumferential surfaces of the nut. The tips of the legs scoop up balls from the track and return balls to the track from the tips of the legs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-269564 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, ball screw devices have been developed in which the legs of the circulation component are inclined relative to the through-hole of the nut. Such legs cannot be fitted into the through-hole, and the tips of the legs are displaced from their intended assembly position. This makes it impossible to smoothly scoop up or return the balls.

[0006] The present disclosure has been made in view of the above, and aims to provide a ball screw device that suppresses positional deviation of the tip of a leg portion. [Means for solving the problem]

[0007] To achieve the above object, a ball screw device according to one aspect of the present disclosure includes a screw shaft, a nut inserted through the screw shaft, a plurality of balls arranged in a track between the screw shaft and the nut, a circulation part having a cylindrical cross-sectional shape for circulating the balls, and a fixed part for fixing the circulation part to the outer peripheral surface of the nut. When viewed from an axial direction parallel to the screw shaft, a direction parallel to an imaginary line connecting the screw shaft and the fixed part is an assembly direction. When viewed from the axial direction, a direction perpendicular to the assembly direction is an intersecting direction. The nut is provided with two through holes that penetrate the nut in the assembly direction and are long in the intersecting direction. The two through holes are arranged on one side and the other side of the intersecting direction, with the imaginary line as a boundary. The circulation part is arranged on the outer peripheral side of the nut and includes a main body portion fixed to the fixed part, two leg portions inserted into the through holes, and two bent portions connecting the main body portion and the leg portions. The inner peripheral surface of the through hole has a pair of opposing surfaces that face each other in the intersecting direction. The pair of opposing surfaces has a first opposing surface that is positioned closer to the imaginary line and a second opposing surface that is positioned further away from the imaginary line. The leg portion is inclined so as to approach the second opposing surface from the first opposing surface toward the tip of the leg portion. The first opposing surface presses the leg portion. The tip of the leg portion is pressed against the second opposing surface.

[0008] According to the present disclosure, the legs are pressed against the first opposing surface and rotate. As a result, the tips of the legs are pressed against the second opposing surface and positioned so as to abut against the second opposing surface. Note that in ball screw devices, for example, due to low precision of the circulation components, the through holes may be formed large, leaving gaps between the legs and the legs. Even in such cases, according to the present disclosure, the tips of the legs are positioned so as to abut against the second opposing surface. Furthermore, because the first opposing surface abuts against the legs, the legs are prevented from rotating so that the tips of the legs move away from the second opposing surface. Therefore, even if the impact of a ball acts on the legs during use of the ball screw device, the tips of the legs remain in abutment against the second opposing surface. As a result, smooth ball scooping and ball return are continuously performed.

[0009] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the second opposing surface has a concave shape with a recessed central portion in the axial direction when viewed from the assembly direction.

[0010] The legs are pressed against the second opposing surface. Therefore, with this configuration, the tips of the legs are aligned so as to fit into the concave recesses in the second opposing surface. This allows the tips of the legs to be positioned at predetermined positions in the axial direction.

[0011] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the second opposing surface has an arc shape when viewed from the assembly direction.

[0012] According to this configuration, the tip of the leg portion is in surface contact with the second opposing surface, making it difficult for the tip to be displaced in the axial direction.

[0013] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the first opposing surface is provided with a pressing surface that presses against the outer circumferential surface of the leg portion, the pressing surface being inclined with respect to the assembly direction and extending along the outer circumferential surface of the leg portion.

[0014] In the present disclosure, the first opposing surface extends in the assembly direction and intersects with the leg portion inclined in the assembly direction. Therefore, the corners of the first opposing surface may press against the leg portion, potentially causing deformation of the leg portion. On the other hand, with the above configuration, the pressing surface comes into surface contact with the leg portion. This prevents the load from concentrating on one part of the leg portion, causing deformation of the leg portion.

[0015] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the through hole extends along the track when viewed from the assembly direction.

[0016] According to this configuration, the through hole fits within one thread of the inner circumferential raceway of the nut and does not interfere with the adjacent inner circumferential raceway, so it can be used even when the circulating part has a small lead.

[0017] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the angle of the inlet and outlet of the circulating component is less than 180° when viewed from the axial direction.

[0018] According to the above configuration, the number of balls arranged on the raceway increases, and the load-bearing capacity of the ball screw device improves.

[0019] In a preferred embodiment of the ball screw device according to the present disclosure, the circulating component is made of a metal material.

[0020] According to this configuration, the durability is superior to that of resin.

[0021] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the main body is divided into two parts in the length direction of the main body.

[0022] According to the present disclosure, a torsional load is generated in the main body due to the rotation of one leg and the rotation of the other leg, but with the above configuration, the torsion is absorbed, and damage to the main body is avoided.

[0023] In a preferred embodiment of the ball screw device according to the present disclosure, the inner peripheral surface of the through hole has a pair of side surfaces facing each other in the axial direction, the diameter of the circulation component is greater than the distance between the pair of side surfaces, and the outer peripheral surface of the leg portion has a pair of flat portions facing the pair of side surfaces and formed by cutting out flat surfaces.

[0024] According to the above-mentioned configuration, a circulation part having a size larger than the distance between the pair of side surfaces can be used, and the strength of the circulation part is improved. Furthermore, since the circulation part has a flat surface, it can be inserted into a through hole. [Effects of the Invention]

[0025] According to the ball screw device of the present disclosure, positional deviation of the tip of the leg portion is suppressed. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a perspective view of a ball screw device according to a first embodiment. [Figure 2] FIG. 2 is a view of the ball screw device of the first embodiment, with the circulating component and the fixed component removed, viewed from the outer periphery of the nut. [Figure 3] FIG. 3 is a cross-sectional view of the nut of the first embodiment cut in the axial direction, as viewed from the inner peripheral side. [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a view of only the circulatory component of the first embodiment taken out and viewed from the axial direction. [Figure 6] FIG. 6 is a view of the nut according to the first embodiment, showing a state in which a circulation component is inserted into a through-hole of the nut, as viewed from the outer periphery side of the nut. [Figure 7] 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a view of the circulation component of the first modification as viewed from the axial direction. [Figure 9] FIG. 9 is a view of the circulatory component of the second modification as viewed from the outside in the assembly direction. [Figure 10]FIG. 10 is a view of the circulation component of the third modification as viewed from the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following detailed description of the preferred embodiments of the present invention will be given with reference to the accompanying drawings. The present disclosure is not limited to the content of the following description. The components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

[0028] (Embodiment 1) Fig. 1 is a perspective view of a ball screw device of embodiment 1. As shown in Fig. 1, the ball screw device 100 of embodiment 1 includes a screw shaft 1 (see Fig. 2), a cylindrical nut 2, a plurality of balls 3 (see Fig. 7), a circulating component 4, and a fixed component 5.

[0029] Fig. 2 is a view of the ball screw device of embodiment 1 with the circulation component and the fixed component removed, viewed from the outer periphery of the nut. As shown in Fig. 2, the screw shaft 1 is a solid rod-shaped component. The screw shaft 1 passes through the nut 2. An outer periphery raceway surface 1a is provided on the outer periphery of the screw shaft 1. Hereinafter, the direction parallel to the axis O1 of the screw shaft 1 will be referred to as the axial direction X.

[0030] Figure 3 is a cross-section of the nut of embodiment 1 cut in the axial direction, viewed from the inner peripheral side. As shown in Figure 3, an inner peripheral surface 10 of the nut 2 is provided with an inner circumferential raceway surface 11. Threads 12 are provided between each thread of the inner circumferential raceway surface 11. The inner circumferential raceway surface 11 faces the outer circumferential raceway surface 1a (see Figure 2). A spiral raceway 7 on which balls 3 roll is formed between the outer circumferential raceway surface 1a and the inner circumferential raceway surface 11 (see Figure 2).

[0031] 4 is a cross-sectional view taken along line IV-IV in FIG. 2. As shown in FIG. 4, the outer peripheral surface 13 of the nut 2 is D-cut. As a result, a flat surface 14 is provided on the outer peripheral surface 13 of the nut 2. The circulating part 4 and the fixed part 5 are mounted on the flat surface 14 (see FIG. 1). The flat surface 14 is perpendicular to an imaginary line K1 extending linearly from the axial center O1. Note that the imaginary line K1 passes through the midpoint between the two through holes 20 when viewed from the axial direction.

[0032] Hereinafter, the direction parallel to the imaginary line K1 will be referred to as the assembly direction Y. Furthermore, within the assembly direction Y, the direction approaching the axial center O1 will be referred to as the inside of the assembly direction Y, and the direction away from the axial center O1 will be referred to as the outside of the assembly direction Y. Additionally, the direction perpendicular to (intersecting with) the imaginary line K1 when viewed from the axial direction will be referred to as the cross direction Z. Within the cross direction Z, the direction approaching the imaginary line K1 will be referred to as the inside of the cross direction Z, and the direction away from the imaginary line K1 will be referred to as the outside of the cross direction Z1.

[0033] As shown in FIG. 4, the nut 2 is provided with a through hole 20 that penetrates the inner peripheral surface 10 and the outer peripheral surface 13 of the nut 2. The through hole 20 extends in the assembly direction Y. The leg portions 42 of the circulable part 4 are arranged in the through hole 20. Thus, two through holes 20 are provided corresponding to the two leg portions 42. When viewed from the axial direction, the two through holes 20 are arranged on one side and the other side of the intersecting direction Z, with the imaginary line K1 as the boundary.

[0034] When viewed from the assembly direction, the two through holes 20, the circulation part 4, and the fixed part 5 are symmetrical with respect to point P (see FIG. 2) on the plane 14. Point P on the plane 14 is located at the center of the axial direction X on the plane 14 and at the center of the transverse direction Z. Therefore, the circulation part 4 and the fixed part 5 can be assembled to the nut 2 even when rotated to point P on the plane 14. In the following explanation, a configuration arranged on one side of point P will be explained as a representative example, and an explanation of a configuration arranged on the other side of point P will be omitted. Furthermore, in the axial direction, the direction approaching point P will be referred to as the inside of the axial direction X, and the direction away from point P will be referred to as the outside of the axial direction X.

[0035] 2, the through hole 20 has a length H2 in the transverse direction Z that is longer than a length H1 in the axial direction X. This allows the leg portions 42 of the circulation component 4 to be arranged in the through hole 20 in a state inclined in the transverse direction Z.

[0036] The inner peripheral surface of the through hole 20 has a pair of side surfaces 21 facing each other in the axial direction X and a pair of opposing surfaces 22 facing each other in the transverse direction Z. The pair of side surfaces 21 has a first side surface 23 arranged closer to the inside of the through hole 20 in the axial direction X and a second side surface 24 arranged closer to the outside of the through hole 20 in the axial direction X. The pair of opposing surfaces 22 has a first opposing surface 25 arranged closer to the inside of the through hole 20 in the transverse direction Z and a second opposing surface 26 arranged closer to the outside of the transverse direction Z. The first side surface 23 and the second side surface 24 are linear. The first opposing surface 25 and the second opposing surface 26 are arc-shaped. As described above, the through hole 20 has a so-called oval shape.

[0037] The through hole 20 is inclined with respect to the transverse direction Z. More specifically, the through hole 20 is inclined so that it is positioned inward in the axial direction X as it moves outward in the transverse direction Z. In other words, the through hole 20 is inclined along the raceway 7. Therefore, as shown in FIG. 3 , the through hole 20 penetrates one thread of the inner circumferential raceway surface 11. Furthermore, the first side surface 23 and the second side surface 24 extend along the thread 12. As described above, the thread 12 is not divided by the through hole 20 and is continuous in the spiral direction.

[0038] As shown in Fig. 2, a recess 16 is provided on the outer peripheral surface 13 of the nut 2 at the edge of the through hole 20. The recess 16 is recessed toward the inner peripheral side of the nut 2 and serves to avoid contact with the bent portion 43 of the circulation component 4. In addition, two female threaded holes (not shown) are provided on the flat surface 14. Screws 6 that fasten the fixing component 5 are threadedly engaged with these female threaded holes (see Fig. 1).

[0039] As shown in Fig. 4, a chamfered pressing surface 27 is provided on a portion of the first opposing surface 25 that is closer to the outside in the assembly direction Y. This pressing surface 27 is formed by chamfering the corner formed by the bottom surface of the recess 16 and the first opposing surface 25. The pressing surface 27 is also inclined so that it is positioned inward in the transverse direction Z as it extends outward in the assembly direction Y. The pressing surface 27 is positioned so that when the leg portion 42 of the circulable component 4 is inserted into the through-hole 20, the pressing surface 27 abuts against the outer peripheral surface of the leg portion 42 and can press the leg portion 42 outward in the transverse direction Z (see Fig. 7).

[0040] Fig. 5 is a view of only the circulation component of embodiment 1 taken out and viewed from the axial direction. As shown in Fig. 5, the circulation component 4 is a cylindrical component, and its internal space serves as a return path 40. The circulation component 4 includes a main body 41 disposed on the outer periphery of the nut 2, two leg portions 42 inserted into the through hole 20, and two bent portions 43 connecting the main body 41 and the leg portions 42. Note that the imaginary circle C shown in Fig. 5 is a circle formed by connecting the centers of the balls 3 disposed on the raceway 7.

[0041] The tip of the leg 42 is provided with a scooping portion 43a that scoops up the balls 3 from the track 7. The angle θ1 of the entrance and exit of the circulating part 4 (the angle at which the two scooping portions 43a scoop up and return the balls 3) is less than 180°.

[0042] The leg portion 42 has a first leg portion 44 that is continuous with the bent portion 43 and a second leg portion 45 that extends further from the first leg portion 44. The first leg portion 44 and the second leg portion 45 are not connected in a straight line but are slightly bent. Specifically, the second leg portion 45 extends parallel to a tangent line D to the imaginary circle C. Meanwhile, the first leg portion 44 is inclined so as to be positioned outside the assembly direction Y with respect to the tangent line D. The scooping portion 43a is provided at the tip of the first leg portion 44. Therefore, in this embodiment, the balls 3 are scooped up by the first leg portion 44, not the second leg portion 45. This reduces the angle θ1 of the entrance and exit of the circulating component 4 compared to when the balls 3 are scooped up by the second leg portion 45. In other words, more balls 3 are arranged on the track 7, improving the load-bearing capacity of the ball screw device 100.

[0043] In addition, in the circulable component 4 of the embodiment, each of the main body 41, the leg 42, and the bent portion 43 is manufactured by bending a cylindrical metal component by press working. Therefore, the cross-sectional shape of the main body 41, the leg 42, and the bent portion 43 is each circular.

[0044] Although the circulative part 4 in embodiment 1 is made of metal, the present disclosure may also be a circulative part made of resin. Furthermore, in the present disclosure, when the circulative part 4 is manufactured from a cylindrical part made of metal, the processing method is not limited to press processing. Furthermore, although the circulative part 4 in embodiment 1 consists of a single part, the present disclosure may also be a circulative part made by joining multiple parts.

[0045] FIG. 6 is a view of the nut from the outer circumferential side, showing the state in which a circulative part is inserted into a through-hole of the nut in embodiment 1. As shown in FIG. 6, the main body 41 is linear. That is, the main body 41 is cylindrical. The main body 41 is placed on the flat surface 14 of the nut 2. The main body 41 is pressed toward the flat surface 14 from the outside in the assembly direction Y by the fixing part 5 (see FIG. 1). This prevents the circulative part 4 from slipping out to the outside in the assembly direction Y. The main body 41 is also positioned so that both ends point toward the two through-holes 20. Therefore, the center line M41 of the main body 41 is inclined with respect to the axial direction X.

[0046] Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. The bent portion 43 is bent and serves to change the traveling direction of the ball 3. As shown in Fig. 7, a portion of the bent portion 43 is disposed in the recess 16 of the nut 2. Therefore, interference between the bent portion 43 and the outer peripheral surface 13 of the nut 2 is avoided.

[0047] The leg portion 42 is disposed in the through hole 20. When viewed from the axial direction, the leg portion 42 is inclined so that it is positioned outward in the intersecting direction Z as it moves inward in the assembly direction Y. Therefore, the leg portion 42 does not extend parallel to the assembly direction Y and has a shape that cannot be fitted into the through hole 20.

[0048] With respect to the rotation directions around the center line M41 of the main body 41, one is referred to as a first rotation direction L1 and the other is referred to as a second rotation direction L2. The outer peripheral surface of the leg 42 has an outer peripheral surface 46 facing the first rotation direction L1 and an inner peripheral surface 47 facing the second rotation direction L2. The outer peripheral surface 46 faces the second opposing surface 26. The inner peripheral surface 47 faces the first opposing surface 25. The outer peripheral surface 46 at the tip of the leg 42 (the tip of the second leg 45) is provided with a corner 48 formed by chamfering the corner. This corner 48 has an arc shape when viewed from the assembly direction Y.

[0049] Next, the through hole 20 and the leg portion 42 will be described in detail. When the circulative component 4 is assembled to the nut 2, the outer peripheral surface of the leg portion 42 comes into contact with the first opposing surface 25. That is, the position of the first opposing surface 25 in the transverse direction Z is set so that it comes into contact with the inner outer peripheral surface 47 of the leg portion 42 (first leg portion 44). As a result, the leg portion 42 receives a load from the outside in the transverse direction Z (see arrow F1). Then, the main body 41 twists about the center line M41, and the leg portion 42 rotates in the first rotation direction L1. As a result, the tip of the leg portion 42 (second leg portion 45) is pressed against the second opposing surface 26 (see arrow F2). From the above, when the circulative component 4 is assembled to the nut 2, the tip (cornered surface 48) of the leg portion 42 (second leg portion 45) is positioned in contact with the second opposing surface 26.

[0050] 7, the other leg 42 (not shown) is pressed against the first opposing surface 25 and rotates in the second rotation direction L2. Therefore, the two legs 42 rotate in different directions, and the distance between the legs 42 (angle θ1) increases.

[0051] Furthermore, the portion of the first opposing surface 25 that comes into contact with the inner outer peripheral surface 47 of the leg portion 42 serves as a pressing surface 27. The pressing surface 27 is an inclined surface that follows the inner outer peripheral surface 47 of the leg portion 42 and is in surface contact with the inner outer peripheral surface 47. This prevents the corners of the first opposing surface 25 from coming into contact with the leg portion 42 and causing deformation of the leg portion 42.

[0052] Furthermore, cornered surfaces 48 are provided at the tips of the legs 42 that are pressed against the second opposing surface 26. Therefore, the tips (cornered surfaces 48) of the legs 42 are in surface contact with the second opposing surface 26. This prevents the load from concentrating on the corners at the tips of the legs 42 and causing deformation of the tips.

[0053] As shown in Figure 6, the axial length H1 (see Figure 2) of the through hole 20 is slightly larger than the diameter of the circulation part 4. In other words, a minute gap is generated between the outer peripheral surface of the leg part 42 and the pair of side surfaces 21. Therefore, even if a manufacturing error occurs in the circulation part 4, the leg part 42 can be reliably inserted into the through hole 20.

[0054] Furthermore, the tip (cornered surface 48) of the leg portion 42 is pressed against the second opposing surface 26 (see F2 in FIG. 7). Therefore, the tip (cornered surface 48) of the leg portion 42 is aligned so as to abut against the portion of the second opposing surface 26 that is recessed furthest outward in the intersecting direction Z. Therefore, the tip (cornered surface 48) of the leg portion 42 is positioned at a predetermined position in the axial direction.

[0055] Furthermore, the corner surface 48 of the leg portion 42 is arc-shaped when viewed from the assembly direction Y. Furthermore, the curvature of the corner surface 48 of the leg portion 42 is the same as the curvature of the second opposing surface 26. Therefore, the corner surface 48 and the second opposing surface 26 abut against each other without any gap. Therefore, even if vibration of the ball 3 occurs in the leg portion 42, the position of the ball 3 is unlikely to shift in the axial direction.

[0056] As described above, according to the ball screw device 100 of the first embodiment, the tip (cornered surface 48) of the leg portion 42 is positioned at a predetermined position in the transverse direction Z and the axial direction X. Therefore, the effort required to position the tip (cornered surface 48) of the leg portion 42 when assembling the circulable component 4 is reduced. Furthermore, because the first opposing surface 25 (pressing surface 27) abuts against the inner outer peripheral surface 47 of the leg portion 42, the leg portion 42 does not rotate in the second rotation direction L2. Therefore, even if vibration of the ball 3 is transmitted to the leg portion 42, the tip of the leg portion 42 is unlikely to separate from the second opposing surface 26. In other words, displacement of the tip of the leg portion 42 is unlikely to occur during use of the ball screw device 100. Furthermore, even if the tip of the leg portion 42 separates from the second opposing surface 26, the tip of the leg portion 42 abuts against the second opposing surface 26 due to elastic deformation. Therefore, smooth scooping up and returning of the ball 3 can be continuously performed.

[0057] As described above, the ball screw device 100 of the first embodiment includes the screw shaft 1, the nut 2 inserted through the screw shaft 1, a plurality of balls 3 arranged in a raceway 7 between the screw shaft 1 and the nut 2, a circulation part 4 having a cylindrical cross section and circulating the balls 3, and a fixed part 5 for fixing the circulation part 4 to the outer peripheral surface 13 of the nut 2. When viewed from the axial direction X parallel to the axis O1 of the screw shaft 1, the direction parallel to the imaginary line K1 connecting the screw shaft 1 and the fixed part 5 is the assembly direction Y. When viewed from the axial direction X, the direction perpendicular to the assembly direction Y is the transverse direction Z. The nut 2 is provided with two through holes 20 that penetrate in the assembly direction Y and are long in the transverse direction Z. The two through holes 20 are arranged on one side and the other side of the transverse direction Z, with the imaginary line K1 as the boundary. The circulation component 4 is disposed on the outer periphery of the nut 2 and includes a main body 41 fixed to the fixed component 5, two leg portions 42 inserted into the through hole 20, and two bent portions 43 connecting the main body 41 and the leg portions 42. The inner periphery of the through hole 20 has a pair of opposing surfaces 22 facing each other in the intersecting direction Z. The pair of opposing surfaces 22 includes a first opposing surface 25 disposed closer to the imaginary line K1 and a second opposing surface 26 disposed further from the imaginary line K1. The leg portions 42 are inclined so as to approach the second opposing surface 26 from the first opposing surface 25 toward the tip of the leg portion 42. The first opposing surface 25 presses the leg portion 42. The tip of the leg portion 42 is pressed against the second opposing surface 26.

[0058] According to the first embodiment, the tip of the leg portion 42 is positioned so as to abut against the second opposing surface 26. Furthermore, because the first opposing surface 25 presses against the leg portion 42, the tip of the leg portion 42 is prevented from moving away from the second opposing surface 26. As a result, the ball 3 can be smoothly and continuously scooped up and returned.

[0059] Moreover, the second opposing surface 26 of the first embodiment has an arc shape when viewed from the assembly direction Y.

[0060] According to this, the tip of the leg portion 42 comes into surface contact with the second opposing surface 26, making it difficult for the tip to be displaced in the axial direction.

[0061] Furthermore, the first opposing surface 25 of the first embodiment is provided with a pressing surface 27 that presses the outer peripheral surface of the leg portion 42. The pressing surface 27 is inclined with respect to the assembly direction Y and extends along the outer peripheral surface of the leg portion 42.

[0062] This allows the pressing surface 27 to come into surface contact with the leg portion 42, preventing deformation of the leg portion 42.

[0063] Furthermore, the through-hole 20 of the first embodiment extends along the track 7 when viewed from the assembly direction Y.

[0064] According to this, the through hole 20 fits into one thread of the inner circumferential raceway surface 11, and the thread 12 is not broken. Therefore, this is applicable even when the circulating part 4 has a small lead.

[0065] Moreover, the angle θ of the inlet and outlet of the circulable part 4 in the first embodiment is less than 180° when viewed from the axial direction.

[0066] According to this, the number of balls 3 arranged on the raceway 7 is increased, and the load resistance of the ball screw device 100 is improved.

[0067] Moreover, the circulating part 4 of the first embodiment is made of a metal material.

[0068] Therefore, the circulating part 4 has superior durability compared to when it is made of a resin material.

[0069] Although the first embodiment has been described above, the present disclosure is not limited to the example shown in the first embodiment. For example, the first opposing surface 25 in the first embodiment has the pressing surface 27, but in the present disclosure, the first opposing surface 25 may press the leg portion 42. Furthermore, the outer peripheral surface 46 at the tip of the leg portion 42 is formed as a corner surface 48, but it may be a rounded surface or may not be chamfered.

[0070] Furthermore, although the second opposing surface 26 in the first embodiment has an arc shape when viewed from the assembly direction Y, in the present disclosure it may have, for example, a triangular shape. That is, the second opposing surface 26 in the present disclosure may have a concave shape with a recessed central portion in the axial direction when viewed from the assembly direction Y. With such a shape, the tip of the leg portion 42 is positioned so as to fit into the concave central portion of the second opposing surface 26. Therefore, the tip of the leg portion 42 is positioned at a predetermined position in the axial direction.

[0071] Furthermore, the circulative part of the present disclosure is not limited to the example shown in embodiment 1. Modified examples of the circulative part will be described below. The following description will focus on the changes.

[0072] (Variation 1) 8 is a view of the circulating device of Modification 1 as viewed from the axial direction. The circulating device 4A of Modification 1 differs from the circulating device 4 of Embodiment 1 in that the leg portion 42A is linear. The center line M42 of the leg portion 42A extends tangentially to the imaginary circle C. According to this circulating device 4A of Modification 1, the angle θ2 formed by the inlet and outlet of the circulating device 4A is less than 180°, but is larger than the angle θ1 of Embodiment 1. In other words, the balls 3 arranged in the track 7 are smaller than those of Embodiment 1, and the durability of the ball screw device 100 is slightly reduced.

[0073] (Variation 2) FIG. 9 is a view of the circulation component of Modification 2 as seen from the outside in the assembly direction. The circulation component 4B of Modification 2 differs from the circulation component 4 of Embodiment 1 in that it is divided into two parts in the longitudinal direction of the main body portion 41B (the direction parallel to the center line M41). That is, the circulation component 4B of Modification 2 is composed of two parts, and the main body portion 41B has a first main body portion 141 and a second main body portion 142. According to the circulation component 4 of Embodiment 1, the main body portion 41 is twisted by the pressure from the first opposing surface 25. On the other hand, according to Modification 2, the first main body portion 141 and the second main body portion 142 rotate in different rotation directions. This reduces the load on the main body portion 41B, making the main body portion 41B less susceptible to damage.

[0074] In Figure 9, in order to make the boundary between the first main body portion 141 and the second main body portion 142 easier to see, a gap is provided between the end portion 141a of the first main body portion 141 and the end portion 142a of the second main body portion 142, but in the present disclosure, the end portion 141a of the first main body portion 141 and the end portion 142a of the second main body portion 142 may also abut.

[0075] (Variation 3) 10 is a view of the circulation device of Modified Example 3 as viewed from the axial direction. The circulation device 4C of Modified Example 3 is similar to the circulation device 4 of Embodiment 1 in that it is manufactured by processing a cylindrical metal part. However, the circulation device 4C of Modified Example 3 differs from the circulation device 4 of Embodiment 1 in that the diameter of the circulation device 4C of Modified Example 3 is larger than the axial length H1 of the through hole 20 (see FIG. 2). The circulation device 4C of Modified Example 3 has high rigidity and improved durability.

[0076] Furthermore, Modification 3 differs from the circulation device 4 of Embodiment 1 in that each of the two leg portions 42C is provided with a pair of flat portions 143 formed by cutting out a flat surface. Note that, although two (a pair of) flat portions 143 are provided for each leg portion 42C, FIG. 10 illustrates the flat portion 143 facing one side of the axial direction X, and does not illustrate the flat portion facing the other side of the axial direction X. Furthermore, the pair of flat portions 143 face a pair of side surfaces 21 (see FIG. 2) of the through hole 20. The pair of flat portions 143 reduces the axial length of the leg portion 42C, allowing it to be inserted into the through hole 20. [Explanation of symbols]

[0077] 100 Ball screw device 1 Screw shaft 2 nuts 3 Ball 4, 4A, 4B, 4C circulating parts 5 Fixing parts 7 orbit 11 Inner raceway surface 14 plane 20 through holes 21 Side 22 Opposite surface 23 First aspect 24 Second side 25 First opposing surface 26 Second opposing surface 27 Pressing surface 40 Return path 41, 41B Main body part 42, 42A Leg part 43 Bending part 43a Lifting part 44 First leg 45 Second leg 46 Outer peripheral surface 47 Inner peripheral surface 48 Angular surface 141 First main body part 142 Second main body part 143 Flat part

Claims

1. A screw shaft, a nut inserted through the screw shaft; a plurality of balls arranged in a raceway between the screw shaft and the nut; a circulation part having a cylindrical cross section that circulates the balls; a fixing part that fixes the circulation part to an outer peripheral surface of the nut; Equipped with When viewed from an axial direction parallel to the screw shaft, a direction parallel to an imaginary line connecting the screw shaft and the fixed part is an assembly direction, When viewed from the axial direction, a direction perpendicular to the assembly direction is a cross direction, The nut is provided with two through holes that penetrate the nut in the assembly direction and are long in the intersecting direction, the two through holes are arranged separately on one side and the other side in the intersecting direction with the imaginary line as a boundary, The circulating part is a main body portion disposed on an outer circumferential side of the nut and fixed to the fixed component; Two legs inserted into the through holes; two bent portions connecting the main body portion and the leg portion; and an inner circumferential surface of the through hole has a pair of opposing surfaces that face each other in the intersecting direction; The pair of opposing surfaces are a first opposing surface disposed near the imaginary line; a second opposing surface disposed away from the imaginary line; and the leg portion is inclined so as to approach the second opposing surface from the first opposing surface toward the tip of the leg portion, the first opposing surface presses the leg portions to increase the angle between the two leg portions; The tip of the leg portion is pressed against the second opposing surface. Ball screw device.

2. The second opposing surface has a concave shape with a recessed central portion in the axial direction when viewed from the assembly direction. The ball screw device according to claim 1 .

3. The second opposing surface has an arc shape when viewed from the assembly direction. The ball screw device according to claim 2 .

4. The first opposing surface is provided with a pressing surface that presses against an outer peripheral surface of the leg portion, The pressing surface is inclined with respect to the assembly direction and extends along the outer circumferential surface of the leg portion. The ball screw device according to any one of claims 1 to 3.

5. The through hole extends along the track when viewed from the assembly direction. The ball screw device according to any one of claims 1 to 4.

6. The angle of the inlet and outlet of the circulating part is less than 180° when viewed from the axial direction. The ball screw device according to any one of claims 1 to 5.

7. The circulating part is made of a metal material. The ball screw device according to any one of claims 1 to 6.

8. The main body is divided into two parts in the longitudinal direction of the main body. The ball screw device according to any one of claims 1 to 7.

9. an inner circumferential surface of the through hole has a pair of side surfaces facing each other in the axial direction; The diameter of the circulating part is greater than the distance between the pair of side surfaces, The outer peripheral surface of the leg portion is provided with a pair of flat portions that are opposed to the pair of side surfaces and are cut out in a flat shape. The ball screw device according to any one of claims 1 to 8.

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