Ball screw device

Abstract

To provide a ball screw device suppressing falling off of a circulation component.SOLUTION: A ball screw device comprises a nut, a screw shaft, a circulation component, and a sleeve. Two leg holes passing through an inner peripheral surface and an outer peripheral surface are formed in the nut. The circulation component has two legs which are inserted into the leg holes, and a return path body disposed on an outer peripheral side of the nut to connect the two legs with each other. The sleeve has a sleeve body with a C-shape as viewed from an axial direction, in which a notch extending in the axial direction parallel to the screw shaft is provided, and two projections projecting from an inner peripheral surface of the sleeve body to a radially inner side, and spaced apart from each other in a circumferential direction. The notch has a width larger than that of the return path body. The sleeve body has a contact surface, which is a portion of the inner peripheral surface, and coming into contact with the return path body. The two projections are spaced apart in the circumferential direction with the contact surface in between. The return path body is disposed between the two projections.SELECTED DRAWING: Figure 9

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 rotational motion into linear motion and linear motion into rotational motion. The ball screw device includes a screw shaft, a nut that is inserted into the screw shaft, a number of balls, and a circulating part. The balls move along a track between the screw shaft and the nut. The circulating part returns the balls that have moved from one end of the track to the other end of the track. When the circulating part is assembled to the nut, it is fixed to the nut by a fixing part.

[0003] An example of a fixing part is a cylindrical sleeve that covers the outer periphery of a nut. The sleeve in Patent Document 1 has a notch extending in the axial direction and is C-shaped when viewed from the axial direction. When such a sleeve is attached to a nut, the sleeve is deformed so that its diameter increases, and the nut is inserted into the inner periphery of the sleeve. After that, when the force applied to the sleeve is released, the sleeve elastically deforms (reduced in diameter) and the sleeve is attached to the nut. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-141465 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sleeve in the above-mentioned patent document is rotatably attached to the nut. Also, the width of the notch in the sleeve may be designed to be large. In such a case, when the sleeve rotates and the notch in the sleeve overlaps with the circulation part in the radial direction, the circulation part may fall off.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a ball screw device that can suppress the falling off of circulating parts. [Means for solving the problem]

[0007] In order to achieve the above object, a ball screw device according to one embodiment of the present disclosure includes a cylindrical nut having an inner peripheral surface and an outer peripheral surface, a screw shaft penetrating the nut, a plurality of balls arranged between the nut and the screw shaft, a circulation part attached to the nut, and a sleeve covering the outer peripheral surface of the nut and the outer peripheral side of the circulation part. The nut is formed with two leg holes penetrating the inner peripheral surface and the outer peripheral surface of the nut. The circulation part has two legs inserted into the leg holes and a return path body arranged on the outer peripheral side of the nut and connecting the two legs. The sleeve has a cut extending in an axial direction parallel to the screw shaft, a C-shaped sleeve body as viewed from the axial direction, and two protrusions protruding radially inward from the inner peripheral surface of the sleeve body and spaced apart from each other in the circumferential direction. The width of the cut is greater than the width of the return path body. The sleeve body has an abutment surface that is a part of the inner peripheral surface and abuts against the return path body. The two protrusions are spaced apart in the circumferential direction with the abutment surface in between, and the return path body is disposed between the two protrusions.

[0008] Since the width of the slit is larger than the width of the return path body, when the sleeve rotates and the slit and the return path body overlap in the radial direction, the circulation part falls off from the slit. Alternatively, the return path body moves radially outward from the slit, and the two legs catch on the sleeve, but the legs cannot scoop up the ball and cannot fulfill the role of the sleeve (fixing the circulation part). However, according to the present disclosure, even if a circumferential load acts on the sleeve, the two protrusions catch on the return path body. Also, the legs of the return path body are inserted into the leg holes, and the circumferential movement is restricted. Therefore, the sleeve does not rotate, and the circulation part is prevented from falling off.

[0009] In a preferred embodiment of the ball screw device according to the present disclosure, the protrusion has a tip portion that is an end portion on the inside in the radial direction. The tip portion is spaced apart from an outer circumferential surface of the nut.

[0010] If the tip of the protrusion abuts against the outer circumferential surface of the nut, if the protrusion is manufactured to be long due to manufacturing errors, the sleeve will bulge outward in the radial direction. This will cause the nut to become larger in the radial direction, resulting in contact with other parts. Furthermore, the abutment surface will be positioned radially outward from the specified position, and the return path body will not abut against the abutment surface. This will cause the circulation component to rattle in the radial direction, preventing smooth transfer of balls between the track and the circulation component. On the other hand, according to the present disclosure, even if there is a manufacturing error, it will be absorbed by the gap between the tip of the protrusion and the outer circumferential surface of the nut. Therefore, the above-mentioned problem does not occur.

[0011] In a preferred embodiment of the ball screw device according to the present disclosure, the distance between the two protrusions is the same as the width of the return path body.

[0012] According to this configuration, circumferential rattling of the sleeve is restricted.

[0013] In a preferred embodiment of the ball screw device according to the aspect of the present disclosure, the two protrusions are disposed in a central portion in a circumferential direction of the sleeve body.

[0014] According to the above configuration, the notch and the circulating part are disposed on opposite sides, so that even if the sleeve rotates, the notch and the circulating part are unlikely to overlap in the circumferential direction.

[0015] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, the outer circumferential surface of the sleeve body is formed with at least one recess that is recessed radially inward and extends in the axial direction.

[0016] According to the present disclosure, when a radially expanding force is applied to the sleeve body, the internal space of the recess is crushed in the circumferential direction, so that the sleeve body is easily deformed and plastic deformation of the sleeve is suppressed.

[0017] In a ball screw device according to an embodiment of the present disclosure, the sleeve body has a central wall disposed in a circumferential center of the sleeve body, the abutment surface and the two protrusions disposed on an inner circumferential side, a pair of connecting portions extending circumferentially outward from each of the pair of protrusions, and a pair of clamping walls extending circumferentially outward from each of the pair of connecting portions. The pair of connecting portions are disposed radially inward from the central wall and the pair of clamping walls. The recess may be provided radially outward from each of the pair of connecting portions.

[0018] In a preferred embodiment of the ball screw device according to the present disclosure, the outer peripheral surface of the nut has an arc-shaped surface when viewed from an axial direction parallel to the screw shaft, and a plane perpendicular to a virtual line extending in a radial direction when viewed from the axial direction. The two leg holes are provided in the plane. The return path body and the two protrusions are disposed radially outward of the plane.

[0019] According to the above configuration, the outer peripheral surface of the nut has a shape that is recessed radially outward from the flat surface. Therefore, even if the return path body and the two protrusions are disposed radially outward from the flat surface, it is possible to prevent the return path body and the sleeve from protruding from the outer peripheral surface of the nut, and to prevent the nut from becoming large in the radial direction.

[0020] In a preferred aspect of the ball screw device according to the aspect of the present disclosure, a flange is provided on an outer circumferential surface of the nut, the flange protruding radially outward from an end portion in the axial direction.

[0021] According to this configuration, the axial end of the sleeve is caught by the flange, and the axial movement of the sleeve is restricted. Effect of the Invention

[0022] According to the ball screw device of the present disclosure, it is possible to prevent circulating parts from falling off. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is an exploded perspective view of a part of the ball screw device according to the first embodiment. FIG. [Diagram 2] FIG. 2 is a view of the nut of the first embodiment as viewed from a direction opposite to the flat surface of the nut. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view of the circulation component of the first embodiment as viewed from the radial outside. [Diagram 5] FIG. 5 is a perspective view of the circulation component of the first embodiment as viewed from the radially inner side. [Figure 6] FIG. 6 is a cross-sectional view showing a state in which the circulation component is assembled to the nut in the first embodiment, and more specifically, a cross-sectional view taken along line VII-VII in FIG. [Figure 7] FIG. 7 is a view showing a state in which a circulation component is assembled to a nut in the first embodiment, as viewed from a direction opposite to a flat surface of the nut. [Figure 8] FIG. 8 is a side view of the common parts constituting the circulatory part of the first embodiment, as viewed from the mating surface. [Figure 9] FIG. 9 is a cross-sectional view of the ball screw device of the first embodiment. [Figure 10] FIG. 10 is a perspective view of the sleeve of the first embodiment. [Figure 11] FIG. 11 is an enlarged view of FIG. [Figure 12] FIG. 12 is a further enlarged view of the return path main body and its vicinity in FIG. [Figure 13] FIG. 13 is a cross-sectional view of a return path body of a comparative example. [Figure 14] FIG. 14 is a cross-sectional view of a ball screw device according to the second embodiment. [Figure 15] FIG. 15 is an enlarged view of a circumferential end portion of the sleeve of the first modification. [Figure 16] FIG. 16 is an enlarged view of a circumferential end portion of a sleeve of the second modification. [Figure 17]FIG. 17 is an enlarged view of a circumferential end portion of a sleeve of the third modified example. [Figure 18] FIG. 18 is a cross-sectional view of the return path main body of the fourth modification taken in an orthogonal direction. [Figure 19] FIG. 19 is a cross-sectional view of the return path main body of the fifth modification taken in an orthogonal direction. [Figure 20] FIG. 20 is a view showing a state in which the circulation component of the sixth modification is attached to a nut, as viewed from a direction opposite to the plane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The embodiment of the invention will be described in detail with reference to the drawings. The present disclosure is not limited to the contents described in the following description. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components described below can be appropriately combined.

[0025] (Embodiment 1) Fig. 1 is an exploded perspective view of a part of a ball screw device of the first embodiment. As shown in Fig. 1, the ball screw device 100 of the first embodiment includes a screw shaft (not shown) (see center line O1 of the screw shaft), a cylindrical nut 1, a plurality of balls 2 (see Fig. 9, etc.), a guide cap type circulation part 3, and a fixed part 5. The screw shaft is a cylindrical part, and an outer circumferential raceway surface is formed on the outer circumferential surface. Hereinafter, the direction parallel to the center line O1 of the screw shaft is referred to as the axial direction X.

[0026] The nut 1 is formed in a cylindrical shape centered on a center line O1. An inner peripheral surface 10 of the nut 1 is formed with an inner peripheral raceway surface 11 that faces an outer peripheral raceway surface of the screw shaft. A spiral raceway is formed between the outer peripheral raceway surface and the inner peripheral raceway surface 11. A plurality of balls 2 are arranged on this raceway.

[0027] Fig. 2 is a view of the nut of the first embodiment as viewed from a direction opposite to the flat surface of the nut. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. As shown in Figs. 2 and 3, the cross-sectional shape of the outer peripheral surface 13 of the nut 1 is D-shaped. Thus, the outer peripheral surface 13 of the nut 1 has an arcuate surface 14 and a flat surface 15. In addition, a ridge line 16 extending in the axial direction X is formed at the boundary between the arcuate surface 14 and the flat surface 15.

[0028] As shown in Fig. 3, the arc surface 14 is formed in an arc shape centered on the center line O1. The dashed line K14 in Fig. 3 is a virtual line when the arc surface 14 is extended in the circumferential direction. The plane 15 is a virtual line K15 extending in the radial direction from the center line O1. In other words, when viewed from the axial direction X, the plane 15 extends linearly in a direction perpendicular to the virtual line K15.

[0029] Hereinafter, the direction parallel to the plane 15 when viewed from the axial direction X (the direction perpendicular to the virtual line K15) is referred to as the orthogonal direction Y. The direction perpendicular to the plane 15 (the direction parallel to the virtual line K15) is referred to as the vertical direction. Among the vertical directions, the direction in which the center line O1 is disposed when viewed from the plane 15 is referred to as the first vertical direction Z1, and the opposite direction is referred to as the second vertical direction Z2.

[0030] The plane 15 is recessed radially inward from the arcuate surface 14. Therefore, a space (hereinafter referred to as an accommodation space 20) located radially inward from the arcuate surface 14 is provided in the second perpendicular direction Z2 (radially outward) of the plane 15.

[0031] Further, two leg holes 17 are formed in the nut 1. The two leg holes 17 penetrate the inner circumferential raceway surface 11 (inner circumferential surface 10) and the flat surface 15 (outer circumferential surface 13). The leg holes 17 communicate the internal space of the nut 1 with the accommodation space 20 (space on the outer circumferential side of the nut 1).

[0032] As shown in Fig. 2, the two leg holes 17 are symmetrical with respect to point P on plane 15. Point P on plane 15 refers to the center of plane 15 in the axial direction X and also the center of plane 15 in the perpendicular direction Y. Edges 17a of leg holes 17 are chamfered (see Fig. 3).

[0033] 2 and 3, flanges 18 are provided at both ends in the axial direction X of the outer peripheral surface 13 of the nut 1. The flanges 18 are circular when viewed from the axial direction. The flanges 18 have a larger diameter than the arcuate surface 14. The arcuate surface 14 and the flat surface 15 are disposed between the two flanges 18.

[0034] Fig. 4 is a perspective view of the circulation part of the first embodiment as viewed from the radial outside. Fig. 5 is a perspective view of the circulation part of the first embodiment as viewed from the radial inside. As shown in Figs. 4 and 5, the circulation part 3 has a return path main body 30 formed in a substantially plate shape, and two legs 31 protruding in the same direction from one surface (bottom surface 32) of the return path main body 30. The return path main body 30 has a bottom surface 32 on which the legs 31 are formed, and an upper surface 33 facing in the opposite direction to the bottom surface 32. The bottom surface 32 and the upper surface 33 are each flat.

[0035] Fig. 6 is a cross-sectional view of the state in which the circulation part is assembled to the nut in the first embodiment, and more specifically, a cross-sectional view taken along line VII-VII in Fig. 7. Such a circulation part 3 is assembled to the nut 1 in the following procedure. First, as shown in Fig. 6, the circulation part 3 is placed in the second vertical direction Z2 of the plane 15 (see the imaginary line K3 in Fig. 6). In addition, the bottom surface 32 of the circulation part 3 is made to face the plane 15. Next, as shown by the arrow A in Fig. 6, the circulation part 3 is moved in the first vertical direction Z1.

[0036] During this movement, the legs 31 are inserted into the leg holes 17. The edges 17a of the leg holes 17 are chamfered to facilitate the insertion of the legs 31. Then, as shown in FIG. 6, when the bottom surface 32 comes into contact with the flat surface 15, the movement in the first vertical direction Z1 is stopped and the assembly of the circulation part 3 is completed. As a result, when the circulation part 3 moves in the direction opposite to the arrow A (the second vertical direction Z2), the circulation part 3 falls off the nut 1.

[0037] When the circulation part 3 is assembled to the nut 1, the upper surface 33 of the return path body 30 faces the second vertical direction Z2. Moreover, the return path body 30 is accommodated in the accommodation space 20 of the nut 1. In other words, the upper surface 33 of the return path body 30 does not protrude radially outward beyond the dashed line K14 (arc surface 14).

[0038] The bottom surface 32 faces the first vertical direction Z1, and abuts against the plane 15. Therefore, the circulation part 3 is positioned so as not to move in the first vertical direction Z1. In addition, the legs 31 are inserted into the leg holes 17. Therefore, the circulation part 3 is positioned so as not to move in a direction parallel to the plane 15.

[0039] A second return path 8 extending in the vertical direction is formed inside the leg 31. An opening 34 and a tongue 35 are formed at the end of the leg 31 in the first vertical direction Z1. The opening 34 opens the second return path 8 in the first vertical direction Z1. The tongue 35 scoops up the ball 2 moving on the track and causes the ball 2 to enter the second return path 8 from the opening 34.

[0040] Fig. 7 is a view showing a state in which the circulation component is assembled to the nut in embodiment 1, as viewed from a direction opposite to the flat surface of the nut. Fig. 8 is a side view showing common components constituting the circulation component of embodiment 1, as viewed from a mating surface. The common components will be described later.

[0041] As shown in Fig. 7, the return path body 30 has a pair of side surfaces 36, 36 facing the perpendicular direction Y. The pair of side surfaces 36, 36 each extend linearly in the axial direction X. A first return path 7 is formed inside the return path body 30. When viewed from the second vertical direction Z2, the first return path 7 extends linearly so as to connect the two leg holes 17. For this reason, the center line O7 of the first return path 7 is not parallel to the center line O1 of the screw shaft but intersects with it.

[0042] As shown in Fig. 8, both ends of the first return path 7 are connected to the second return path 8. In other words, the first return path 7 connects the two second return paths 8 to each other. According to this circulation device 3, when the ball 2 enters one of the second return paths 8, the ball 2 moves along the second return path 8 in the second vertical direction Z2 (see arrow B1). Also, when the ball 2 moves from the second return path 8 to the first return path 7, the ball 2 moves along the first return path 7 (see arrow B2).

[0043] Subsequently, when the ball 2 moves from the first return path 7 to the other second return path 8, the ball 2 moves along the second return path 8 in the first vertical direction Z1 (see arrow B3). Then, the ball 2 returns to the orbit from the opening 34 of the leg portion 31. Hereinafter, the passage combining the first return path 7 and the two second return paths 8 is referred to as the return path 6.

[0044] Moreover, the shape of the circulable part 3 in this embodiment is point-symmetric with respect to point P on the plane 15. In other words, the circulable part can be assembled even in a state rotated 180°, which can reduce the labor required for assembly.

[0045] 4 and 5, the circulative part 3 is composed of a first part 301 and a second part 302 that are divided into two parts in an orthogonal direction along the center line of the return path 6. The shape of the circulative part 3 is point-symmetric with respect to a point P on the plane 15, and when the first part 301 is rotated 180° with respect to the point P, it becomes the second part 302. In other words, the first part 301 and the second part 302 are simply the common part 300 with the orientation changed. Therefore, according to this embodiment, it is possible to save the effort of manufacturing two parts with different shapes.

[0046] 8, a concave surface 311 is formed on a mating surface 310 of the common part 300. When two common parts 300 (first part 301 and second part 302) are combined, the internal space of this concave surface 311 forms the return path 6. In addition, the mating surface 310 is provided with a protrusion 313 and a recess 314 into which the protrusion 313 fits. Therefore, when the first part 301 and the second part 302 are combined, no misalignment occurs.

[0047] In this embodiment, an example is given in which the circulating part 3 is composed of two parts (first part 301 and second part 302), but the present disclosure is not limited to this, and the circulating part 3 may be composed of three or more parts, or the circulating part 3 may be a single part that cannot be divided.

[0048] Fig. 9 is a cross-sectional view of the ball screw device of embodiment 1. As shown in Fig. 9, the fixed part 5 is a sleeve 50 that fits onto the outer periphery of the nut 1. The sleeve 50 has a cylindrical sleeve body 51 and two protrusions 53 that protrude radially inward from an inner periphery 52 of the sleeve body 51.

[0049] The sleeve body 51 covers the outer circumferential side of the return path body 30 of the circulation part 3. The inner circumferential surface 52 of the sleeve body 51 abuts against the upper surface 33 of the return path body 30. This restricts the circulation part 3 from moving in the second vertical direction Z2, that is, from falling off the nut 1. Hereinafter, the part of the inner circumferential surface 52 of the sleeve body 51 that abuts against the return path body 30 is referred to as the abutment surface 57. The abutment surface 57 extends in the axial direction X and the perpendicular direction Y (see FIG. 10). The sleeve body 51 is C-shaped when viewed from the axial direction. A notch 54 extending in the axial direction is provided between the circumferential ends 51a, 51a of the sleeve body 51. The notch 54 is disposed on the opposite side of the two protrusions 53 across the center line O1. Further, end faces 51c, 51c of the ends 51a, 51a of the sleeve body 51 each extend in the radial direction. Further, in this embodiment, the angle θ1 that the cut 54 occupies in the sleeve body 51 is approximately 90°.

[0050] Furthermore, an axial end face 51b (see FIG. 1) of the sleeve body 51 abuts against the flange 18 of the nut 1 from the axial direction X. Therefore, even if a load in the axial direction X acts on the sleeve 50, movement of the sleeve 50 in the axial direction X is restricted. In other words, the sleeve 50 is prevented from falling off the nut 1 in the axial direction X.

[0051] The sleeve 50 is attached to the nut 1 in the following manner. First, a force is applied to the circumferential ends 51a, 51a of the sleeve body 51 so that they are separated from each other, and the sleeve body 51 is expanded in diameter. The sleeve body 51 is deformed so that the size of the notch 54 is larger than the outer diameter of the nut 1. Next, the nut 1 is moved so as to pass through the notch 54, and the sleeve 50 is attached from the radial outside of the nut 1. Then, the force applied to the sleeve body 51 is removed, and the sleeve body 51 is reduced in diameter (elastically deformed). As a result, the inner peripheral surface 52 of the sleeve body 51 abuts against the arc surface 14 (outer peripheral surface 13) of the nut 1, and the sleeve 50 fits on the outer peripheral side of the nut 1. As a result, the sleeve 50 is fixed to the nut 1. Note that the method of attaching the sleeve 50 to the nut 1 is not limited to the above-mentioned method. For example, the sleeve body 51 is deformed so that the sleeve body 51 has a larger diameter than the flange 18 of the nut 1. The nut 1 may then be moved in the axial direction to be inserted into the inside of the sleeve body 51 .

[0052] In this embodiment, when the sleeve 50 is attached to the nut 1, the sleeve body 51 has an elastic deformation force that reduces the diameter. As a result, even if a force that expands the diameter of the sleeve body 51 acts on the sleeve body 51, the sleeve body 51 resists this force. Therefore, the sleeve body 51 is unlikely to expand in diameter, and the sleeve 50 is prevented from falling off the nut 1.

[0053] Further, the portions of the sleeve body 51 that are in contact with the arcuate surface 14 are only the circumferential ends 51a, 51a of the sleeve body 51. In other words, a minute gap (not shown) is generated between the arcuate surface 14 and the portions of the sleeve body 51 other than the ends 51a, 51a. Therefore, the portions of the sleeve body 51 that are in contact with the nut 1 are a total of three points: the circumferential ends 51a, 51a and the abutment surface 57 (see arrows C1, C2, C3 in FIG. 9).

[0054] Then, due to an elastic deformation force acting on the sleeve body 51, the ends 51a, 51a of the sleeve body 51 are pressed against the arcuate surface 14 (see arrows C1 and C2 in FIG. 9). The abutment surface 57 is also pressed against the return path body 30 (see arrow C3 in FIG. 9). The circulation part 3 is pressed against the abutment surface 57 and maintains a state of abutment against the plane 15. This allows the balls 2 to be transferred smoothly between the track and the circulation part 3.

[0055] Further, the width of the notch 54 is M1. The width M1 of the notch 54 is larger than the width M2 in the orthogonal direction Y of the plane 15. As shown in FIG. 7, the width M3 of the circulation part 3 in the orthogonal direction Y in the state where it is assembled to the nut 1 is smaller than the width M2 in the intersecting direction of the plane 15. In other words, the width M3 of the circulation part 3 is smaller than the width M1 of the notch 54. For this reason, when the sleeve 50 rotates and the notch 54 and the circulation part 3 overlap in the radial direction, the circulation part 3 falls off from the notch 54.

[0056] 9, the two protrusions 53 are disposed circumferentially spaced apart from each other with a contact surface 57 therebetween. The return path body 30 of the circulation part 3 is disposed between the two protrusions 53. Therefore, when a circumferential load acts on the sleeve body 51, one of the two protrusions 53 gets caught on the return path body 30, restricting the rotation of the sleeve 50. This prevents the sleeve 50 from rotating and the notches 54 from overlapping with the circulation part 3 in the radial direction, i.e., prevents the circulation part 3 from falling off the notches 54.

[0057] The distance between the two protrusions 53 is the same as the width of the return path main body 30. In other words, the two protrusions 53 always abut against the pair of side surfaces 36 of the return path main body 30, and rattling of the sleeve 50 in the circumferential direction is restricted.

[0058] The two protrusions 53 are disposed in the circumferential center of the sleeve body 51. That is, the two protrusions 53 and the circulation part 3 are disposed on opposite sides of the cutout 54 across the center line O1. For this reason, the amount of rotation of the sleeve 50 required for the circulation part 3 and the cutout 54 to overlap in the radial direction is large. Therefore, even if the engagement between the protrusions 53 and the return path body 30 is released, it is difficult for the circulation part 3 and the cutout 54 to overlap in the radial direction.

[0059] Fig. 10 is a perspective view of the sleeve of embodiment 1. As shown in Fig. 10, the two protrusions 53 extend in the axial direction, and the contact area between the protrusions 53 and the side surface 36 is large in the axial direction. For this reason, the protrusions 53 are difficult to release from the return path main body 30.

[0060] Fig. 11 is an enlarged view of Fig. 9. As shown in Fig. 11, the two protrusions 53 are disposed in the accommodation space 20. This prevents the sleeve 50 from expanding radially outward (increasing in size radially outward) due to the protrusions 53. This prevents the nut 1 from coming into contact with other components while the ball screw device 100 is in operation.

[0061] The projection 53 has a tip portion 58 which is an end portion on the inside in the radial direction. The tip portion 58 is separated from the plane 15. In other words, a gap is provided between the tip portion 58 and the plane 15. This provides the following two effects.

[0062] First, assuming that the tip 58 of the projection 53 abuts against the flat surface 15 of the nut 1, if the projection 53 is manufactured to be long due to a manufacturing error, a part of the sleeve 50 will bulge outward in the radial direction. On the other hand, according to this embodiment, even if the projection 53 is manufactured to be long due to a manufacturing error, this is absorbed by the gap between the tip 58 and the flat surface 15. In other words, the nut 1 is prevented from becoming large in the radial direction outward.

[0063] Secondly, if the tip 58 of the projection 53 abuts against the flat surface 15 of the nut 1, if the projection 53 is manufactured longer due to a manufacturing error, the abutment surface 57 will be positioned radially outward from a predetermined position. As a result, the abutment surface 57 will not abut against the return path main body 30. In other words, the circulation part 3 will rattle in the radial direction, and the ball 2 will not be smoothly transferred between the raceway and the circulation part 3. On the other hand, according to this embodiment, even if there is a manufacturing error, it is absorbed by the gap between the tip 58 and the flat surface 15, and the return path main body 30 will reliably abut against the abutment surface 57. Therefore, the radial rattle of the circulation part 3 is suppressed.

[0064] The sleeve body 51 also has a central wall 60 arranged in the circumferential center of the sleeve body 51, a pair of connecting portions 61, 61 extending circumferentially outward from each of the pair of protrusions 53, and a pair of clamping walls 62, 62 extending circumferentially outward from each of the pair of connecting portions 61, 61.

[0065] The central wall 60 has an abutment surface 57 and two protrusions 53 on its inner circumferential side. The central wall 60 and the connection portion 61 are connected via the protrusions 53. The connection portion 61 is disposed radially inward from the central wall 60 and the clamping wall 62. Therefore, two recesses 56 are provided radially outward from the connection portion 61, which are recessed radially inward from the outer circumferential surface 55 of the sleeve body 51. When a force is applied to expand the diameter of the sleeve body 51, the internal space of the recesses 56 is crushed in the circumferential direction (see arrow D in FIG. 11). Therefore, the sleeve body 51 is easily deformed, and plastic deformation of the sleeve 50 is suppressed.

[0066] The thickness of the connection portion 61 is the same as the thickness W1 of the sandwiching wall 62. The thickness W2 of the central wall 60 is greater than the thickness W1 of the sandwiching wall 62. Therefore, when a force is applied to expand the diameter of the sleeve body 51, the central wall 60 is less likely to deform than the connection portion 61 and the sandwiching wall 62. In other words, plastic deformation of the central wall 60 is suppressed. If the central wall 60 were to plastically deform, the distance between the two protrusions 53 would increase, and the sleeve 50 would potentially rattle in the circumferential direction. Therefore, in this embodiment, rattling in the circumferential direction of the sleeve 50 due to plastic deformation of the central wall 60 is avoided.

[0067] Moreover, the amount of protrusion W3 (see FIG. 3) of the flange 18 protruding radially outward from the arcuate surface 14 is greater than the thickness W1 of the clamping wall 62. As a result, even in a state in which a minute gap (not shown) is generated between the clamping wall 62 (sleeve main body 51) and the arcuate surface 14, the sleeve main body 51 does not protrude radially outward beyond the flange 18. In addition, the connection portion 61 and the central wall 60 are disposed within the accommodation space 20, and do not protrude radially outward beyond the flange 18.

[0068] 11 is a line extending from the inner circumferential surface 61a of the connection portion 61 to the center in the orthogonal direction Y. The tip portion 58 of the projection 53 is located beyond the imaginary line K61 in the first vertical direction Z1. That is, the projection 53 protrudes radially inward from the inner circumferential surface 61a of the connection portion 61. In other words, the vertical thickness of the projection 53 is greater than that of the connection portion 61. That is, the contact area between the projection 53 and the side surface 36 is greater in the radial direction (vertical direction). For this reason, it is difficult for the projection 53 to be released from its engagement with the return path main body 30.

[0069] Fig. 12 is an enlarged view of the return path main body and its vicinity in Fig. 11. Next, details of the return path main body 30 will be described. As shown in Fig. 12, the return path main body 30 includes a cylindrical wall portion 40 having the first return path 7 formed therein, a first opening 41, and a second opening 42.

[0070] The size of the first return path 7 of the wall portion 40 is slightly larger than the diameter of the ball 2. Therefore, the ball 2 moves smoothly through the first return path 7. Moreover, the width of the first return path 7 in the orthogonal direction Y is L1.

[0071] The first opening 41 penetrates a portion of the wall portion 40 that is radially outside (in the second vertical direction Z2) of the first return path 7. The first opening 41 also extends along the first return path 7 (see FIG. 4). The first opening 41 is closed by an inner circumferential surface 52 of the sleeve body 51 from the second vertical direction Z2.

[0072] The width L2 of the first opening 41 in the orthogonal direction Y is smaller than the width L1. Therefore, a part of the wall portion 40 remains in the second vertical direction Z2 (radially outward) of the first return path 7. The width L2 of the first opening 41 is set to a size that prevents the ball 2 from jumping out radially outward from the first opening 41. Therefore, the ball 2 does not come into contact with the inner circumferential surface 52 of the sleeve main body 51. In other words, the sleeve 50 of this embodiment does not function as a radially outer wall portion of the first return path 7.

[0073] As a result, the ball 2 moving along the first return path 7 moves along the first return path 7 while contacting a portion of the remaining wall portion 40. Hereinafter, the portion of the wall portion 40 remaining in the second vertical direction Z2 (radially outside) of the first return path 7 will be referred to as an outer wall 43.

[0074] The first opening 41 is provided in the center of the outer wall 43 in the orthogonal direction Y. Therefore, the outer wall 43 is composed of two partial outer walls 44 separated in the orthogonal direction Y. A surface 44a of the partial outer wall 44 in the second vertical direction Z2 constitutes a part of the upper surface 33 of the return path body 30 and is flat. In addition, the surface 44a of the partial outer wall 44 in the second vertical direction Z2 abuts against the sleeve 50.

[0075] The surface 44b of the partial outer wall 44 in the first vertical direction Z1 surrounds the first return path 7 in the second vertical direction Z2 and serves as a contact surface that comes into contact with the ball 2. The surface 44b of the partial outer wall 44 in the first vertical direction Z1 moves away from the upper surface 33 of the return path body 30 as it moves from the center (first opening 41) in the orthogonal direction Y toward the outside in the orthogonal direction Y.

[0076] Each of the two partial outer walls 44 has a smaller thickness in the vertical direction (radial direction) toward the first opening 41. Therefore, the portion of the partial outer wall 44 with the smallest vertical (radial) thickness is the end portion closest to the first opening 41. Furthermore, the thickness H1 of the end portion closest to the first opening 41 of the partial outer wall 44 is a thickness that provides sufficient rigidity to prevent deformation due to contact with the ball 2. Therefore, the outer wall 43 (the two partial outer walls 44) does not deform due to contact with the ball 2.

[0077] The second opening 42 penetrates a portion of the wall 40 on the radial inside (first vertical direction Z1) of the first return path 7. The width L3 of the second opening 42 in the orthogonal direction Y is the same as the width L1. Therefore, the portion of the wall 40 in the first vertical direction Z1 of the first return path 7 (hereinafter, may be referred to as the bottom wall) is entirely cut out. In addition, the second opening 42 is blocked from the first vertical direction Z1 by the flat surface 15 (outer peripheral surface 13) of the nut 1. Therefore, the ball 2 moving through the first return path 7 moves through the first return path 7 while contacting the flat surface 15 of the nut 1.

[0078] 8, the first opening 41 is defined by a first notch 341 formed in the mating surface 310 of the common component 300. The second opening 42 is defined by a second notch 342 formed in the mating surface 310 of the common component 300.

[0079] Next, a description will be given of the effect of the return path main body 30 having the first opening 41 and the second opening 42. In addition, in this description, a return path main body (comparative example) not having the first opening 41 and the second opening 42 will be used.

[0080] FIG. 13 is a cross-sectional view of the return path body of the comparative example. The broken line in FIG. 13 is the return path body 30 of the first embodiment. In addition, in FIG. 13, the center line O7 of the first return path 7 of the first embodiment and the center line O207 of the first return path 207 of the comparative example are illustrated so as to overlap. As shown in FIG. 13, the return path body 230 of the comparative example differs from the first embodiment in that it does not have the first opening 41 and the second opening 42. Therefore, the return path body 230 of the comparative example has an outer wall 243 and a bottom wall 245 that are not open.

[0081] The surface 243a of the outer wall 243 in the second vertical direction Z2 is flat as in the first embodiment, and constitutes a part of the upper surface 233 of the return path main body 230. The surface 243b of the outer wall 243 in the first vertical direction Z1 is an arcuate surface along the ball 202 as in the first embodiment. Therefore, in the comparative example, the central part of the outer wall 243 in the orthogonal direction Y has the smallest thickness in the vertical direction. Also, the thickness H2 of the central part of the outer wall 243 in the orthogonal direction Y is the same as the thickness H1 (see FIG. 12) to avoid deformation due to contact with the ball 202.

[0082] The bottom wall 245 is a portion of the wall portion 240 that is disposed radially inward of the first return path 207. The bottom wall 245 has a surface 245a in a first vertical direction Z1 and a surface 245b in a second vertical direction Z2. The surface 245a constitutes a part of the bottom surface 232 of the return path main body 230. The surfaces 245a and 245b are each flat. Thus, the thickness H3 of the bottom wall 245 in the vertical direction is constant. Moreover, the thickness H3 of the bottom wall 245 is the same as the thickness H1 (see FIG. 12) in order to avoid deformation due to contact with the ball 202.

[0083] From the above, the upper surface 233 of the return path body 230 of the comparative example is located in the second vertical direction Z2 by a thickness H4 from the upper surface 33 of the return path body 30 of embodiment 1. Also, the bottom surface 232 of the return path body 230 of the comparative example is located in the first vertical direction Z1 by a thickness H3 from the bottom surface 32 of the return path body 30 of embodiment 1. Therefore, the return path body 30 of embodiment 1 is made smaller in the vertical direction (radial direction) by the sum of the thicknesses H4 and H3.

[0084] In the first embodiment, the portion of the return path body 30 whose thickness is less than H1 due to the radial reduction in size is cut out by the first opening 41 and the second opening 42. This prevents the wall portion 40 from being deformed by contact with the ball 2, preventing the ball 2 from moving smoothly.

[0085] As described above, the ball screw device 100 of the first embodiment includes a cylindrical nut 1 having an inner peripheral surface 10 and an outer peripheral surface 13, a screw shaft penetrating the nut 1, a plurality of balls 2 arranged between the nut 1 and the screw shaft, a circulation part 3 attached to the nut 1, and a sleeve 50 covering the outer peripheral surface 13 of the nut 1 and the outer peripheral side of the circulation part 3. The nut 1 is formed with two leg holes 17 penetrating the inner peripheral surface 10 and the outer peripheral surface 13. The circulation part 3 has two legs 31 inserted into the leg holes 17 and a return path body 30 arranged on the outer peripheral side of the nut 1 and connecting the two legs 31 to each other. The sleeve 50 has a cut 54 extending in the axial direction parallel to the screw shaft, a sleeve body 51 that is C-shaped when viewed from the axial direction, and two protrusions 53 that protrude radially inward from the inner peripheral surface 52 of the sleeve body 51 and are spaced apart from each other in the circumferential direction. The width M1 of the cut 54 is larger than the width M4 of the return path body 30. The sleeve body 51 has an abutment surface 57 that is part of the inner circumferential surface 52 and abuts against the return path body 39. The two protrusions 53 are spaced apart in the circumferential direction with the abutment surface 57 in between. The return path body 30 is disposed between the two protrusions 53.

[0086] According to the first embodiment, the sleeve 50 is difficult to rotate, and the circulation part 3 can be prevented from falling off.

[0087] Above, the description has been given of embodiment 1. Next, a description will be given of embodiment 2, which is a partial modification of embodiment 1. Note that the description of embodiment 2 will focus on the differences from embodiment 1.

[0088] (Embodiment 2) 14 is a cross-sectional view of a ball screw device of the second embodiment. The sleeve 150 of the second embodiment differs from the first embodiment in that the tip surface 158a of the protrusion 153 is on an extension of the inner peripheral surface 61a of the connection portion 61. That is, the protrusion 153 of the second embodiment does not exceed the imaginary line K61 (see FIG. 11), and the protrusion amount in the first vertical direction Z1 (radially inward) is small. According to the second embodiment, although the contact area between the protrusion 153 and the side surface 36 is small in the radial direction (vertical direction), the protrusion 153 abuts against the side surface 36 of the return path main body 30, and the rotation of the sleeve 150 is suppressed.

[0089] Although each embodiment has been described above, the present disclosure is not limited to the examples described in the embodiments. For example, the width M1 of the cut 54 in the first embodiment is larger than the width M3 of the circulation part 3, but the present disclosure is not limited to this. For example, the width M1 of the cut 54 may be smaller than the width M3 of the circulation part 3 and larger than the width M4 of the return path body 30 in the perpendicular direction Y (see FIG. 7). According to this example, when the cut 54 and the return path body 30 overlap in the radial direction, the return path body 30 passes through the cut 54 and moves radially outward. The two legs 31 move radially outward from the leg holes 17 and get caught on the sleeve 50. In this state, the legs 31 cannot scoop up the ball 2, and the role of the sleeve 50 (fixing the circulation part 3) cannot be fulfilled. Therefore, when the width M1 of the cut 54 is larger than the width M4 of the return path body 30 (M1>M4), the effect of the present disclosure (prevention of rotation of the sleeve 50) is effective.

[0090] In the embodiment, the angle θ1 (see FIG. 9) of the notch 54 in the sleeve body 51 is about 90°, but the present disclosure is not limited to the angle (90°) shown in the embodiment. However, if the angle θ1 is 180° or more, the sleeve 50 cannot be attached to the nut 1. Therefore, in the present disclosure, it is essential that the angle θ1 is less than 180° (θ1<180°). In the present disclosure, the preferred range of the angle θ1 of the notch 54 is 75° to 180°.

[0091] In addition, in the present disclosure, the tip portion 58 of the projection 53 may abut against the outer circumferential surface 13 (flat surface 15) of the nut 1. Even with such a projection 53, the rotation of the sleeve 50 can be restricted.

[0092] In addition, in the present disclosure, the distance between the two protrusions 53 does not have to be the same as the width M4 of the return path body. For example, even if the distance between the two protrusions 53 is greater than the width M4 of the return path body, the protrusions 53 are caught by the return path body 30, and the rotation of the sleeve 50 is restricted.

[0093] Furthermore, in the present disclosure, the two protrusions 53 do not have to be disposed at the circumferential center (central wall 60) of the sleeve body 51. In other words, even if the two protrusions 53 are shifted in the circumferential direction from the circumferential center of the sleeve body 51, the protrusions 53 are caught by the return path body 30, and the rotation of the sleeve 50 is restricted.

[0094] Furthermore, in the present disclosure, the recess 56 does not necessarily have to be provided on the outer circumferential surface 55 of the sleeve body 51 .

[0095] In addition, in the present disclosure, the sleeve body 51 does not have to have an elastic deformation force that reduces the diameter when the sleeve body 51 is attached to the nut 1. In addition, although an example has been given in which only the circumferential ends 51a, 51a of the sleeve body 51 abut against the arcuate surface 14, in the present disclosure, the sleeve body 51 may also abut against the arcuate surface 14 including portions other than the ends 51a, 51a.

[0096] Furthermore, the shape of the pair of end faces 51c, 51c of the sleeve body 51 is not limited to the example described in the embodiment, and may be as described below.

[0097] (Modification 1, Modification 2, Modification 3) FIG. 15 is an enlarged view of the circumferential end of the sleeve of the first modification. FIG. 16 is an enlarged view of the circumferential end of the sleeve of the second modification. FIG. 17 is an enlarged view of the circumferential end of the sleeve of the third modification. As shown in FIG. 15, a pair of end faces 251c, 251c of the sleeve body 251 of the first modification are parallel to the vertical direction. As shown in FIG. 16, a pair of end faces 351c, 351c of the sleeve body 351 of the second modification are formed in an arc shape when viewed from the axial direction. As shown in FIG. 17, a pair of end faces 451c, 451c of the sleeve body 451 of the third modification are inclined surfaces that protrude into the cut 54 as they approach the outer circumferential side of the sleeve body 451.

[0098] In addition, the rotatable part of the present disclosure may be as shown in the following modified examples.

[0099] (Variation 4) Fig. 18 is a cross-sectional view of the return path body of Modification 4 cut in the orthogonal direction. As shown in Fig. 18, the return path body 30A of Modification 4 differs from the first embodiment in that the width L4 of the second opening 42A is smaller than the width L1 of the first return path 7. Therefore, the bottom wall 45A remains on the wall portion 40A. In addition, the bottom wall 45A has two partial bottom walls 46 separated in the orthogonal direction Y.

[0100] On the other hand, the surface 46a of the partial bottom wall 46 in the second vertical direction Z2 is a contact surface surrounding the first return path 7 in the first vertical direction Z1. Moreover, the surface 46a of the partial bottom wall 46 in the second vertical direction Z2 moves away from the bottom surface 32 of the return path main body 30 as it moves from the center (second opening 42A) in the orthogonal direction Y toward the outside in the orthogonal direction Y. Therefore, the two partial bottom walls 46 each have a smaller thickness in the vertical direction (radial direction) as it approaches the second opening 42. Moreover, the thickness H5 of the end of the partial bottom wall 46 near the second opening 42A is the same as the thickness H1 to avoid deformation due to contact with the ball 2.

[0101] As described above, according to the fourth modification, as in the first embodiment, the radial thickness of the return path body 30A is smaller than that in the case where the first opening 41 and the second opening 42A are not provided. Moreover, the outer wall 43 and the bottom wall 45A are not deformed even when they come into contact with the ball 2. According to the fourth modification, since the bottom wall 45A is provided, the radial thickness is larger than that of the first embodiment by the thickness H5 of the bottom wall 45A.

[0102] (Variation 5) FIG. 19 is a cross-sectional view of the return path body of the fifth modification cut in an orthogonal direction. As shown in FIG. 19, the return path body 30B of the fifth modification differs from the first embodiment in that the width L5 of the first opening 41B is the same as the width L1 of the first return path 7. Therefore, the wall portion 40B does not have the outer wall 43 (partial outer wall 44). According to the fifth modification, the radial thickness is smaller than that of the first embodiment by the thickness H1. In addition, since the outer wall 43 (see FIG. 12) and the bottom wall 45A (see FIG. 18) are not present, the wall portion does not deform due to contact with the ball 2. Furthermore, in the fifth modification, the ball 2 moves through the first return path 7 while contacting the inner circumferential surface 52 (contact surface 57) of the sleeve 50. Therefore, the sleeve 50 of the fifth modification plays the role of the radially outer wall portion of the first return path 7.

[0103] (Variation 6) FIG. 20 is a view showing a state in which the circulation part of the sixth modification is assembled to the nut, viewed from a direction opposite to the plane. As shown in FIG. 20, the return path body 30C of the sixth modification differs from the first embodiment in that a part 37 of the side surface 36C is parallel to the first return path 7. According to the sixth modification, the remaining part 38 of the side surface 36C (the part parallel to the axial direction X) abuts against the protrusion 53. Thus, in the sixth modification, the rotation of the sleeve 50 is restricted, as in the first embodiment. With regard to the width M4 in the orthogonal direction Y of the return path body 30 of the sixth modification, imaginary lines are extended in the axial direction from each of the parts of the return path body 30C that are located most outside in the orthogonal direction Y (the remaining parts 38 of the side surface 36C), and the distance between the parallel imaginary lines is the width M4. Similarly, the width M3 of the circulative part 3 in the orthogonal direction Y is determined by extending imaginary lines in the axial direction from each of the parts of the circulative part 3 that are located outermost in the orthogonal direction Y (the surfaces of the legs 31 that face outward in the orthogonal direction Y), and the distance between these parallel imaginary lines is the width M3.

[0104] Although the modified example of the circulation part has been described above, the circulation part of the present disclosure is not limited to a guide cap type circulation part. For example, it may be a circulation part such as a top or a deflector attached from the outer periphery side of the nut. In addition, in the embodiment, the nut is provided with flanges on both ends, but in the present disclosure, a flange may be provided on one end of the nut. Or, it may be a nut that is not provided with a flange at all. In addition, it may be a nut that is provided with a gear, a spline, or the like instead of a flange. In addition, in the present embodiment, the sleeve body 51 is configured not to protrude radially outward from the flange 18, but in the present disclosure, the sleeve body 51 may be configured to protrude radially outward from the flange 18.

[0105] In addition, in the present disclosure, a separate part may be provided on the outer periphery of the sleeve, and this separate part may prevent the sleeve from falling off the nut. In addition, the material of the circulating part of the present disclosure may include metal, resin, etc., but the present disclosure is not limited thereto. Furthermore, when the circulating part is manufactured from metal, an example of a manufacturing method may include MIM (Metal Injection Molding), but the present disclosure may be manufactured using other manufacturing methods. In addition, the material of the sleeve may include resin, metal, etc., as with the resin part, but the present disclosure is not limited thereto. When the sleeve is manufactured from metal, iron-based or stainless steel-based materials may be used, but the present disclosure may be manufactured using other metals.

[0106] The present disclosure may also be implemented in the following combinations: (1) A cylindrical nut having an inner circumferential surface and an outer circumferential surface; A screw shaft passing through the nut; A plurality of balls disposed between the nut and the screw shaft; A circulation part attached to the nut; A sleeve that covers an outer peripheral surface of the nut and an outer peripheral side of the circulation component; Equipped with The nut is formed with two leg holes penetrating the inner peripheral surface and the outer peripheral surface of the nut, The circulating part is Two legs inserted into the leg holes; A return path body that is disposed on an outer peripheral side of the nut and connects the two leg portions to each other; having The sleeve is A sleeve body having a cut extending in an axial direction parallel to the screw axis and having a C-shape when viewed from the axial direction; Two protrusions protruding radially inward from an inner circumferential surface of the sleeve body and spaced apart from each other in the circumferential direction; having The width of the cut is greater than the width of the return path body, The sleeve body has an abutment surface that is a part of the inner circumferential surface and abuts against the return path body, The two protrusions are spaced apart from each other in the circumferential direction with the contact surface in between, The return path body is disposed between the two protrusions. Ball screw device. (2) The protrusion has a tip portion which is a radially inner end portion, The tip portion is spaced from the outer peripheral surface of the nut. A ball screw device as described in (1). (3) The distance between the two protrusions is equal to the width of the return path body. A ball screw device as described in (1) or (2). (4) The two protrusions are disposed at the center of the sleeve body in the circumferential direction. A ball screw device according to any one of (1) to (3). (5) The outer circumferential surface of the sleeve body is formed with at least one recess that is recessed radially inward and extends in the axial direction. A ball screw device according to any one of (1) to (4). (6) The sleeve body includes: a central wall disposed at a circumferential center of the sleeve body, the central wall having the contact surface and the two protrusions on an inner peripheral side; a pair of connection portions extending circumferentially outward from each of the pair of projections; A pair of sandwiching walls extending circumferentially outward from each of the pair of connection portions; having The pair of connection portions are disposed radially inward of the central wall and the pair of clamping walls, The recesses are provided on the radially outer sides of the pair of connecting portions. A ball screw device as described in (5). (7) The outer peripheral surface of the nut is When viewed from an axial direction parallel to the screw shaft, an arcuate surface having an arc shape; A plane perpendicular to a virtual line extending in a radial direction when viewed from the axial direction; having The plane is provided with the two leg holes, The return path body and the two protrusions are disposed radially outward of the plane. A ball screw device according to any one of (1) to (6). (8) The nut has an outer circumferential surface provided with a flange that protrudes radially outward from the axial end. A ball screw device according to any one of (1) to (7). [Explanation of symbols]

[0107] 100 Ball screw device 1 Nut 2. Ball 3 Rotable parts 5 Fixing parts 6 Return Route 7, 207 1st Return Road 8 Second Return Path 13 Outer surface 14 Circular Surface 15 plane 17 Leg hole 18 Flange 30, 30A, 30B, 230 Return path body 31 Legs 32, 232 Bottom 33, 233 top surface 34 Aperture 40, 40A, 40B wall 41, 41B 1st opening 42, 42A 2nd opening 43, 243 Exterior wall 44 Partial exterior wall 45A, 245 bottom wall 46 Partial bottom wall 50 Sleeve 51 Sleeve body 53 Protrusion 54 Cut 56 Recess 57 Contact surface 58 Tip 60 Central wall 61 Connection 62 Clamping wall 300 Common Parts 301 1st part 302 2nd Part 310 Mating surface 311 Concave

Claims

1. A cylindrical nut having an inner circumferential surface and an outer circumferential surface; A screw shaft passing through the nut; A plurality of balls disposed between the nut and the screw shaft; A circulation part attached to the nut; A sleeve that covers an outer peripheral surface of the nut and an outer peripheral side of the circulation component; Equipped with The nut is formed with two leg holes penetrating the inner peripheral surface and the outer peripheral surface of the nut, The circulating part is Two legs inserted into the leg holes; A return path body that is disposed on an outer circumferential side of the nut and connects the two legs to each other; having The sleeve is A sleeve body having a cut extending in an axial direction parallel to the screw axis and having a C-shape when viewed from the axial direction; Two protrusions protruding radially inward from an inner circumferential surface of the sleeve body and spaced apart from each other in the circumferential direction; having The width of the cut is greater than the width of the return path body, The sleeve body has an abutment surface that is a part of the inner circumferential surface and abuts against the return path body, The two protrusions are spaced apart from each other in the circumferential direction with the contact surface therebetween, The return path body is disposed between the two protrusions. Ball screw device.

2. The protrusion has a tip portion which is a radially inner end portion, The tip portion is spaced from the outer peripheral surface of the nut. The ball screw device according to claim 1 .

3. The distance between the two protrusions is equal to the width of the return path body. The ball screw device according to claim 1 .

4. The two protrusions are disposed at the center of the sleeve body in the circumferential direction. The ball screw device according to claim 1 .

5. The outer circumferential surface of the sleeve body is formed with at least one recess that is recessed radially inward and extends in the axial direction. The ball screw device according to claim 1 .

6. The sleeve body includes: a central wall disposed at a circumferential center of the sleeve body, the central wall having the contact surface and the two protrusions on an inner peripheral side; a pair of connection portions extending circumferentially outward from each of the pair of projections; A pair of sandwiching walls extending circumferentially outward from each of the pair of connection portions; having The pair of connection portions are disposed radially inward of the central wall and the pair of clamping walls, The recesses are provided on the radially outer sides of the pair of connecting portions. The ball screw device according to claim 5.

7. The outer peripheral surface of the nut is When viewed from an axial direction parallel to the screw shaft, an arcuate surface having an arc shape; A plane perpendicular to a virtual line extending in a radial direction when viewed from the axial direction; having The plane is provided with the two leg holes, The return path body and the two protrusions are disposed radially outward of the plane. The ball screw device according to any one of claims 1 to 6.

8. The nut has an outer circumferential surface provided with a flange that protrudes radially outward from the axial end. The ball screw device according to any one of claims 1 to 6.

Images