Ball screw

Abstract

To provide a ball screw that facilitates pre-load adjustment between two adjacent nuts and is reducible in cost.SOLUTION: A pre-load adjustment mechanism 1 provided between a first nut 21 and a second nut 31 comprises: an annular recessed part 29 which is formed on the first nut 21; an annular projection part 39 which is formed on the second nut 31 and is fitted rotatably in the annular recessed part 29; a first slit 24 which is formed in an outer peripheral wall of the annular recessed part 29; a second slit 34 which is formed in the annular projection part 39 to communicate with the first slit 24 along the same radial direction; a through hole 25 which penetrates the first nut 21 in an axial direction to communicate with the first slit 24 and the second slit 34; a pre-load adjustment component 41 which has a pre-load imparting part 45 arranged straddling the first slit 24 and the second slit 34 and a rotary shaft part 43 supported rotatably in the through hole 25; and a nut fixing bolt 51 which fixes the first nut 21 and the second nut 31 in a relative rotation-disabled state.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a ball screw having a preload adjustment mechanism between a nut that is screwed onto a screw shaft. [Background technology]

[0002] Among the ball screws used in machine tools and the like, there is a ball screw that has a preload applying mechanism (preload adjusting mechanism) interposed between adjacent nuts that are screwed onto the screw shaft via multiple rolling elements to ensure rigidity and improve positioning accuracy during cutting work, and preloads the adjacent nuts.

[0003] As a ball screw capable of adjusting the preload, a ball screw equipped with a preload applying mechanism that allows the preload to be adjusted without using a spacer has been proposed as described in Patent Document 1. In this preload applying mechanism, a convex portion extending in the axial direction is provided on the contact side of one of the two nuts, a concave portion capable of accommodating the convex portion is provided on the contact side of the other nut, four pressing surfaces are formed in the concave portion, and four female threads are provided on the outer peripheral surface of the other nut at positions facing the pressing surfaces. Then, four pressing screws that are screwed into the female threads are tightened to press the four pressing surfaces, thereby shifting the phase of the two nuts relative to each other around the axis, thereby making it possible to adjust the preload.

[0004] Patent Document 2 discloses a preload recovery device for a ball screw that can recover the preload when the preload is reduced without providing an external drive unit. The preload application mechanism in this preload recovery device includes a spacer that is inserted between adjacent nuts and applies an initial preload, a pair of opposing rings that are arranged in a receiving portion formed on one end face of the adjacent nuts and that are movable in the axial direction and have inclined faces on their opposing faces that change in width in the radial direction, a plurality of pressing pieces that engage between the inclined faces of the pair of opposing rings, and a threaded portion that moves the pressing pieces in the radial direction. When the preload between the adjacent nuts is reduced, the pair of opposing rings are moved axially outward by the pressing pieces, thereby recovering the preload between the adjacent nuts.

[0005] Patent Document 3 discloses a ball screw device that can quickly adjust the preload according to the situation without polluting the surrounding environment, and that can be made compact and simple. The biasing mechanism (preload adjustment mechanism) in this ball screw device includes a plurality of pressure balls provided at equal intervals in the circumferential direction between the inclined surfaces formed on the opposing ends of the first nut and the second nut, a pressure ring made of a magnetic material arranged to surround the plurality of pressure balls and having an inner peripheral surface formed as a pressure surface made of an inclined surface that gradually inclines toward the center in one axial direction, and an electromagnet that moves the pressure ring in the axial direction by magnetic force, thereby pressing the pressure balls toward the center with the pressing surface. The electromagnet generates a reaction force along the axial direction between the first nut and the second nut, thereby applying a preload. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6561586 [Patent Document 2] Patent No. 6540266 [Patent Document 3] Patent No. 7183708 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the preload applying mechanism of Patent Document 1, when adjusting the preload, it is necessary to tighten a set screw into the female thread of one nut from the outer periphery side of the other nut. Therefore, when the ball screw is attached to a machine tool or the like, it is necessary to remove the ball screw from the bracket of the machine tool or the like, making the adjustment work troublesome. Furthermore, in the preload applying mechanisms of Patent Documents 2 and 3, it is necessary to provide a spacer or the like between adjacent nuts, the thickness of which needs to be adjusted (polished), which is a factor in increasing costs.

[0008] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a ball screw that allows easy adjustment of the preload between two adjacent nuts and reduces costs. [Means for solving the problem]

[0009] The above object of the present invention can be achieved by the following configuration. a screw shaft having a spiral screw shaft side raceway groove formed on an outer circumferential surface; two nuts each having a spiral nut-side raceway groove formed on an inner peripheral surface thereof so as to face the screw-shaft-side raceway groove, and each being fitted around the screw shaft and abutting against each other; a plurality of balls rolling in a ball rolling path formed by the nut side raceway groove and the screw shaft side raceway groove of each of the two nuts; a preload adjustment mechanism provided between the two nuts; A ball screw comprising: The preload adjustment mechanism includes: An annular recess formed on an axial end surface of one of the two nuts on a contact side; an annular protrusion formed on an axial end surface of the other nut on the contact side of the other of the two nuts and rotatably fitted into the annular recess; A first slit is formed in an outer peripheral wall of the annular recess along a radial direction; A second slit is formed in the annular convex portion so as to communicate with the first slit along the same radial direction; a through hole formed between an axial end surface of the abutment side and an axial end surface of the non-abutment side in the one nut or the other nut, and communicating with at least one of the first slit and the second slit; a preload adjusting component including a preload applying portion disposed across the first slit and the second slit, and a rotating shaft portion rotatably passing through the through hole and provided at one end thereof for applying a rotational force to the preload applying portion; a nut fixing bolt having a threaded portion passing through a bolt through hole provided in either the one nut or the other nut from an axial end face side on the opposite contact side and screwed into either the other nut or the one nut, thereby fixing the one nut and the other nut so that they cannot rotate relative to each other; A ball screw comprising: Effect of the Invention

[0010] According to the present invention, it is possible to provide a ball screw that allows easy adjustment of the preload between two adjacent nuts and reduces costs.

[0011] The present invention has been briefly described above. Furthermore, the details of the present invention will be further clarified by reading the following description of the embodiment of the present invention (hereinafter, referred to as "embodiment") with reference to the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an overall perspective view of a ball screw according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Diagram 3] FIG. 3 is an exploded perspective view of the ball screw shown in FIG. [Figure 4] FIG. 4 is a perspective view of one of the nuts shown in FIG. 3 as viewed from the contact side. [Diagram 5] FIG. 5 is a side view of the non-contact side of one of the nuts shown in FIG. [Figure 6] FIG. 6 is a perspective view of the other nut shown in FIG. 3 as viewed from the contact side. [Figure 7] FIG. 7 is a side view of the contact side of the other nut shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. [Figure 9]FIG. 9 is a sectional view for explaining the operation of the ball screw according to the first embodiment shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view of a ball screw provided with a preload adjusting part according to the first modification, taken along the line VIII-VIII in FIG. [Figure 11] FIG. 11 is a cross-sectional view of a ball screw provided with a preload adjusting part according to Modification 2, and corresponds to the cross section taken along the line VIII-VIII in FIG. [Figure 12] FIG. 12 is a cross-sectional view of a ball screw provided with a preload adjusting part according to the third modification, taken along the line VIII-VIII in FIG. [Figure 13] FIG. 13 is a cross-sectional view of a ball screw according to a second embodiment of the present invention, taken along line VIII-VIII in FIG. [Figure 14] FIG. 14 is a perspective view of the preload adjusting part shown in FIG. [Figure 15] FIG. 15 is a perspective view of one nut in a ball screw according to a third embodiment of the present invention, as viewed from the contact side. [Figure 16] FIG. 16 is a side view of the contact side of one of the nuts shown in FIG. [Figure 17] FIG. 17 is a cross-sectional view of the ball screw according to the third embodiment, and corresponds to the cross-section taken along line VIII-VIII in FIG. [Figure 18] FIG. 18 is a sectional view for explaining the operation of the ball screw according to the third embodiment shown in FIG. [Figure 19] FIG. 19 is a cross-sectional view of a ball screw according to a fourth embodiment of the present invention, and corresponds to the cross-section taken along line VIII-VIII in FIG. [Figure 20] FIG. 20 is a cross-sectional view of a ball screw according to a fifth embodiment of the present invention, and corresponds to the cross-section taken along line VIII-VIII in FIG. [Figure 21] FIG. 21 is an exploded perspective view of a ball screw according to a sixth embodiment of the present invention. [Figure 22] FIG. 22 is a side view of the contact side of one of the nuts shown in FIG. [Figure 23] FIG. 23 is a side view of the contact side of the other nut shown in FIG. [Figure 24] FIG. 24 is a cross-sectional view of the ball screw according to the sixth embodiment, and corresponds to the cross-section taken along line VIII-VIII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ball screw according to an embodiment of the present invention will be described in detail below with reference to the drawings. (First embodiment) First, a ball screw according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG. Fig. 1 is a perspective view of a ball screw 11 according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view taken along the line II-II in Fig. 1. Fig. 3 is an exploded perspective view of the ball screw 11 shown in Fig. 1.

[0014] The ball screw 11 of this first embodiment is a double-nut type ball screw, and as shown in Figures 1 to 3, includes a screw shaft 13, a first nut 21 and a second nut 31 fitted onto the screw shaft 13, a plurality of balls 61, and a preload adjustment mechanism 1 provided between the first nut 21 and the second nut 31. As shown in FIG. 2, the screw shaft 13 has a spiral screw shaft side raceway groove 14 formed on its outer circumferential surface.

[0015] Fig. 4 is a perspective view of the first nut 21 shown in Fig. 3 as viewed from the contact side. Fig. 5 is a side view of the anti-contact side of the first nut 21 shown in Fig. 4. 3 to 5, the metallic first nut 21 is composed of a cylindrical body 22 having a flange portion 23 formed at the end on the non-contact side (right side in FIG. 2), and a spiral nut-side raceway groove 27 facing the screw shaft-side raceway groove 14 is formed on the inner peripheral surface of this cylindrical body 22. Furthermore, an annular recess 29 is formed on an axial end face 28a on the contact side (left side in FIG. 2) of the first nut 21 serving as one nut.

[0016] A first slit 24 is formed as one of the slits opening along the radial direction by cutting out a part of the outer circumferential wall that defines this annular recess 29. The first slit 24 has a pair of opposing walls 24a that face each other in the circumferential direction at a predetermined interval, and the bottom surface between the pair of opposing walls 24a is continuous with the bottom surface of the annular recess 29.

[0017] Furthermore, the first nut 21 is formed with a through hole 25 penetrating between the axial end face 28a on the contact side and the axial end face 28b on the non-contact side. The through hole 25 has a circular cross section and extends parallel to the central axis of the nut. An opening end 25a of the through hole 25 at the axial end face 28a on the contact side opens to the bottom surface of the annular recess 29 and the bottom surface of the first slit 24.

[0018] A bolt through hole 26 is formed at an axially symmetrical position of the through hole 25 on either side of the central axis of the nut, penetrating between an axial end face 28a on the contact side and an axial end face 28b on the non-contact side of the first nut 21. The bolt through hole 26 has an opening cross section in the shape of an arc centered on the central axis of the nut and extends parallel to the central axis of the nut. A counterbore 26a is formed on the opening edge of the bolt through hole 26 at the axial end face 28b on the non-contact side.

[0019] Fig. 6 is a perspective view of the second nut 31 shown in Fig. 3 as viewed from the contact side. Fig. 7 is a side view of the contact side of the second nut shown in Fig. 6. Fig. 8 is a cross-sectional view taken along the line VIII-VIII in Fig. 1. Fig. 9 is a cross-sectional view for explaining the operation of the ball screw 11 according to the first embodiment shown in Fig. 8.

[0020] 3 and 6 and 7, the second nut 31 made of metal is composed of a cylindrical body 32 having no flange portion, and a spiral nut-side raceway groove 37 facing the screw shaft-side raceway groove 14 is formed on the inner peripheral surface of this cylindrical body 32. Furthermore, an annular convex portion 39 rotatably fitted into the annular concave portion 29 is formed on an axial end face 38a on the abutment side (right side in FIG. 2) of the second nut 31 as the other nut, and an axial end face 38b is formed on the non-abutment side (left side in FIG. 2).

[0021] A second slit 34 is cut out and formed in a part of the annular protrusion 39 as the other slit that opens so as to communicate with the first slit 24 along the same radial direction when the annular protrusion 39 is fitted into the annular recess 29. The second slit 34 has a pair of opposing walls 34a that face each other in the circumferential direction at a predetermined distance, and the bottom surface between the pair of opposing walls 34a is continuous with the axial end surface 38a on the contact side.

[0022] Furthermore, a threaded hole 36 is drilled in an axial end face 38a of the second nut 31 at a position symmetrical to the second slit 34 across the central axis of the nut. The threaded hole 36 extends parallel to the central axis of the nut, and when the annular protrusion 39 is fitted into the annular recess 29, an opening end of the threaded hole 36 faces the bolt through hole 26 of the first nut 21.

[0023] The multiple balls 61 are spherical bodies made of steel such as alloy steel, and roll on ball rolling paths formed by the nut-side raceway grooves 27, 37 and the screw shaft-side raceway groove 14 in the first nut 21 and the second nut 31. The nut-side raceway grooves 27, 37 and the screw shaft-side raceway groove 14 have a cross-sectional shape of a Gothic arc that is a substantial V shape formed by combining two identical circular arcs with different centers of curvature.

[0024] The second nut 31, whose annular protrusion 39 is rotatably fitted into the annular recess 29 of the first nut 21, is positioned adjacent to the first nut 21 on the opposite side of the flange portion 23 of the first nut 21 and capable of rotating relative to the first nut 21 around the central axis. In addition, in the first nut 21 and the second nut 31, a circulation path (not shown) is formed to return the ball 61 from one end in the axial direction to the other end, and the ball 61 is circulated through this circulation path.

[0025] Furthermore, a preload adjustment mechanism 1 is provided between the first nut 21 and the second nut 31, as shown in Fig. 2. This preload adjustment mechanism 1 is composed of the above-mentioned first slit 24 and second slit 34, a preload adjustment part 41 (see Fig. 3) rotatably supported in the through hole 25 of the first nut 21, and a nut fixing bolt 51 (see Fig. 3) rotatably supported in the bolt through hole 26 of the first nut 21.

[0026] 2 and 3, the preload adjustment product 41 has a round bar-shaped rotating shaft portion 43 and a substantially rectangular parallelepiped preload applying portion 45 whose outer circumferential surface along the rotation direction is chamfered. One end of the rotating shaft portion 43 is connected to the longitudinal center of the preload applying portion 45. A hexagonal hole 47 is drilled in the other end of the rotating shaft portion 43. When the rotating shaft portion 43 is inserted from the opening end 25a of the through hole 25, the hexagonal hole 47 of the rotating shaft portion 43 is exposed from the opening end 25b of the through hole 25 at the axial end face 28b on the non-contact side. Thus, the preload adjusting part 41 can be rotated by a hexagonal wrench or the like from the axial end face 28b on the non-contact side of the first nut 21.

[0027] It should be noted that the hexagonal hole 47 drilled in the other end of the rotating shaft portion 43 is not limited to this, and may have any shape, such as a square hole, a Torx (registered trademark) hole, a Phillips groove, a flathead groove, etc., as long as the rotating shaft portion 43 can be turned with a tool. In addition, the other end of the rotating shaft portion 43 may be formed into a square prism shape or a hexagonal prism shape so that it can be turned with a wrench or the like.

[0028] In addition, when the rotating shaft portion 43 is inserted into the through hole 25 and the annular convex portion 39 of the second nut 31 is fitted into the annular concave portion 29 of the first nut 21, the preload applying portion 45 is disposed across the first slit 24 and the second slit 34, as shown in Fig. 8. In other words, the preload applying portion 45 is disposed in the space defined by the first slit 24 and the second slit 34.

[0029] Here, the predetermined distance between the pair of opposing walls 24a of the first nut 21 according to the first embodiment is wider than the predetermined distance between the pair of opposing walls 34a of the second nut 31. The pair of opposing walls 34a of the second nut 31 are in a state in which there is almost no gap between them and both side walls of the preload applying portion 45. In contrast, the pair of opposing walls 24a of the first nut 21 are in a state in which there is a gap between them that allows them to swing relative to both side walls of the preload applying portion 45.

[0030] 2 and 3, the nut fixing bolt 51 is a hexagonal socket bolt having a hexagonal hole 55 in its cylindrical head. The nut fixing bolt 51 is inserted into the bolt through hole 26 from the axial end face 28b side of the non-contact side of the first nut 21, and a threaded portion 53 passing through the bolt through hole 26 is screwed into the threaded hole 36 of the second nut 31. In other words, the nut fixing bolt 51 can be rotated by a hexagonal wrench or the like from the axial end face 28b side of the non-contact side of the first nut 21, and the first nut 21 and the second nut 31 can be bolted together so as not to rotate relative to each other.

[0031] Next, the effects of the ball screw 11 of the first embodiment will be described. First, when assembling the ball screw 11 of this first embodiment, the rotating shaft portion 43 of the preload adjustment part 41 is inserted into the through hole 25 from the axial end face 28a side on the abutting side of the first nut 21, and the preload applying portion 45 is placed in the first slit 24.

[0032] Then, the axial end face 28a on the contact side of the first nut 21 and the axial end face 38a on the contact side of the second nut 31 are brought into contact with each other. At this time, the annular recess 29 of the first nut 21 fits into the annular protrusion 39 of the second nut 31 such that the preload applying portion 45 is disposed in the second slit 34 of the second nut 31. In addition, when the abutment side axial end face 28a and the abutment side axial end face 38a are in contact with each other, the bottom surface of the annular recess 29 and the tip surface of the annular protrusion 39 are configured not to come into contact with each other. Thereafter, the combined first nut 21 and second nut 31 are screwed onto the screw shaft 13 via the plurality of balls 61 .

[0033] Next, the preload adjusting part 41 is rotated clockwise using a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43. Then, as shown in Fig. 9, the preload applying part 45 presses one of the opposing walls 34a of the second slit 34, and the phase of the second nut 31 can be shifted in the R direction around the axis relative to the first nut 21.

[0034] At this time, the lead direction of the first nut 21 and the second nut 31 is set so that the direction in which the second nut 31 is shifted in the R direction relative to the first nut 21 is the direction in which preload is applied. Therefore, when the preload-adjusting part 41 is rotated in the clockwise direction, preload is applied, and when the preload-adjusting part 41 is rotated in the counterclockwise direction, the preload is released.

[0035] In other words, in the ball screw 11 of this first embodiment, by rotating the preload adjustment part 41 in a clockwise direction, the preload application part 45 presses one of the opposing walls 34a in the second slit 34, and a preload can be applied between the adjacent first nut 21 and second nut 31 by a force that shifts the phase of the second nut 31 in the R direction around the axis relative to the first nut 21.

[0036] Then, for example, with the rotational force of the preload adjusting part 41 being torque-controlled with a torque wrench or the like to obtain a predetermined preload load, the nut fixing bolt 51 is inserted into the bolt through hole 26 from the axial end face 28b side opposite the contact side of the first nut 21. The nut fixing bolt 51 inserted into the bolt through hole 26 has a threaded portion 53 that passes through the bolt through hole 26 screwed into the threaded hole 36 of the second nut 31, thereby bolting the first nut 21 and the second nut 31 together so that they cannot rotate relative to each other.

[0037] Here, since the bolt through hole 26 has an opening cross section that is arc-shaped, the bolt can be fastened even if the phase of the second nut 31 changes relative to the first nut 21. Also, since the tightening force of the nut fixing bolt 51 is applied only to the contact surfaces between the first nut 21 and the second nut 31 (the axial end face 28a on the contact side and the axial end face 38a on the contact side), it does not significantly affect the preload between the first nut 21 and the second nut 31.

[0038] Therefore, according to the ball screw 11 of the first embodiment, the preload can be adjusted without using a spacer by rotating the preload-adjusting part 41 to adjust the preload by shifting the phase between the adjacent first nut 21 and second nut 31. That is, the ball screw 11 does not require thickness adjustment (grinding) of the spacer, which allows for cost reduction. Furthermore, the ball screw 11 can apply and release preload by changing the rotation direction of the preload-adjusting part 41, making the assembly work easy.

[0039] Moreover, the ball screw 11 of the first embodiment has a fitting structure in which the annular convex portion 39 of the second nut 31 is fitted into the annular concave portion 29 of the first nut 21. Therefore, the ball screw 11, which is a double nut system, suppresses nut outer diameter runout and does not require adjustment work.

[0040] Furthermore, the ball screw 11 of the first embodiment is compact since the preload adjustment mechanism 1 is not provided on the outer periphery of the nut. Furthermore, the ball screw 11 of the first embodiment has a structure in which the preload adjustment mechanism 1 is operated from the non-contact side of the first nut 21, and the preload adjustment mechanism 1 can be provided at any phase in the outer circumferential direction of the nut. Therefore, any type of circulation part that is provided on the outer circumferential surface of the nut to form a circulation path can be used.

[0041] In addition, in the ball screw 11 of the first embodiment, the preload can be adjusted by rotating the preload adjusting part 41 from the non-contact side of the first nut 21 where the flange portion 23 is formed, and then the first nut 21 and the second nut 31 can be bolted together from the same non-contact side with the nut fixing bolt 51 so that they cannot rotate relative to each other. Thus, even when the ball screw 11 is attached to a machine, the preload can be adjusted without removing the first nut 21 and the second nut 31 from the bracket. As a result, even when the preload is lost due to wear, the preload can be easily restored.

[0042] Therefore, according to the ball screw 11 of the first embodiment described above, it is possible to provide a ball screw that allows easy preload adjustment between the adjacent first nut 21 and second nut 31 and enables cost reduction.

[0043] (Modification) Next, ball screws equipped with preload adjusting parts according to Modifications 1 to 3 will be described with reference to FIGS. 10 to 12 are cross-sectional views of ball screws 11A to 11C equipped with preload adjusting parts 41A to 41C according to first to third modified examples, and correspond to the cross section VIII-VIII in FIG.

[0044] The ball screws 11A to 11C equipped with preload adjusting parts 41A to 41C according to the modifications 1 to 3 are different from the ball screw 11 of the above-described first embodiment in that the preload adjusting part 41 is changed to the preload adjusting parts 41A to 41C, respectively. Since the other configurations are substantially similar to those of the above-described first embodiment, the same reference numerals are used and detailed description will be omitted.

[0045] As shown in FIG. 10, in a ball screw 11A, a preload-adjusting part 41A is used instead of the preload-adjusting part 41 of the first embodiment. The preload adjusting part 41A has a round bar-shaped rotating shaft portion 43 and a preload applying portion 45A provided at one end of the rotating shaft portion 43 and having an X-shaped cross section. A hexagonal hole 47 is drilled in the other end of the rotating shaft portion 43, and the preload adjusting part 41A can be rotated from the axial end face 28b side opposite the contact side of the first nut 21 using a hexagonal wrench or the like.

[0046] When the preload adjusting part 41A is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43, the preload applying part 45A presses one of the opposing walls 34a of the second slit 34. Thus, a preload can be applied between the adjacent first nut 21 and second nut 31 by the force that shifts the phase of the second nut 31 in the R direction around the axis relative to the first nut 21.

[0047] As shown in FIG. 11, in a ball screw 11B, a preload-adjusting part 41B is used instead of the preload-adjusting part 41 of the first embodiment. The preload adjusting part 41B has a round bar-shaped rotating shaft portion 43 and a preload applying portion 45B provided at one end of the rotating shaft portion 43 and having an elliptical cross section. A hexagonal hole 47 is drilled in the other end of the rotating shaft portion 43, and the preload adjusting part 41B can be rotated from the axial end face 28b side opposite the contact side of the first nut 21 using a hexagonal wrench or the like.

[0048] When the preload adjusting part 41B is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43, the preload applying part 45B presses one of the opposing walls 34a of the second slit 34. Thus, a preload can be applied between the adjacent first nut 21 and second nut 31 by the force that shifts the phase of the second nut 31 in the R direction around the axis relative to the first nut 21.

[0049] As shown in FIG. 12, in a ball screw 11C, a preload-adjusting part 41C is used instead of the preload-adjusting part 41 of the first embodiment. The preload adjusting part 41C has a round bar-shaped rotating shaft portion 43 and a preload applying portion 45C provided at one end of the rotating shaft portion 43 and having an H-shaped cross section. A hexagonal hole 47 is drilled in the other end of the rotating shaft portion 43, and the preload adjusting part 41C can be rotated from the axial end face 28b side opposite the contact side of the first nut 21 using a hexagonal wrench or the like.

[0050] When the preload adjusting part 41C is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43, the preload applying part 45C presses one of the opposing walls 34a of the second slit 34. Thus, a preload can be applied between the adjacent first nut 21 and second nut 31 by the force that shifts the phase of the second nut 31 in the R direction around the axis relative to the first nut 21.

[0051] Therefore, according to the ball screws 11A to 11C equipped with the preload adjustment parts 41A to 41C relating to these modified examples 1 to 3, it is possible to provide a ball screw that facilitates preload adjustment between the adjacent first nut 21 and second nut 31, as with the ball screw 11 of the first embodiment described above, and that allows for cost reduction.

[0052] Second embodiment Next, a ball screw according to a second embodiment of the present invention will be described with reference to FIGS. Fig. 13 is a cross-sectional view of a ball screw 11D according to a second embodiment of the present invention, taken along the line VIII-VIII in Fig. 1. Fig. 14 is a perspective view of a preload adjusting part 41D shown in Fig. 13.

[0053] The ball screw 11D according to the second embodiment differs from the ball screw 11 of the above-described first embodiment in that the preload adjusting part 41 is changed to a preload adjusting part 41D, and the position of the through hole 25 formed in the first nut 21 is shifted to the outer periphery of the cylindrical body 22. Other configurations are substantially similar to those of the above-described first embodiment, so the same reference numerals are used and detailed description is omitted.

[0054] In a ball screw 11D according to the second embodiment, as shown in FIG. 13, a preload-adjusting part 41D is used instead of the preload-adjusting part 41 of the first embodiment. In addition, the through hole 25 formed in the first nut 21 has its penetration position displaced toward the outer periphery of the cylinder 22, and the opening end 25a at the axial end face 28a on the abutment side opens to the bottom face of the first slit 24.

[0055] 14, the preload adjusting part 41D has a round bar-shaped rotating shaft part 43 and a substantially rectangular parallelepiped preload applying part 45D whose outer circumferential surface along the rotation direction is chamfered. Here, one end of the rotating shaft part 43 is connected to one longitudinal end of the preload applying part 45D. A hexagonal hole 47 is drilled in the other end of the rotating shaft portion 43, and the preload adjusting part 41D can be rotated from the axial end face 28b side opposite the contact side of the first nut 21 using a hexagonal wrench or the like.

[0056] Here, in the preload adjusting part 41D, one end of the rotating shaft part 43 is connected to one longitudinal end of the preload applying part 45D. Therefore, when the rotating shaft part 43 is rotated, the preload applying part 45D has a rotation center at one longitudinal end, and the rotation radius of the other longitudinal end, which is the swing end, can be increased.

[0057] The preload adjusting part 41D has a rotating shaft part 43 rotatably supported in a through hole 25 whose opening end 25a opens to the bottom surface of the first slit 24. Thus, the preload adjusting part 41D can press the opposing wall 34a of the second nut 31 with the swing end of the preload applying part 45D, which has a larger rotation radius. As a result, the ball screw 11D can shift the phase of the second nut 31 more significantly in the R direction around the axis relative to the first nut 21, and the range of preload adjustment can be expanded.

[0058] Therefore, according to the ball screw 11D of the second embodiment, similar to the ball screw 11 of the first embodiment described above, it is possible to provide a ball screw that allows for easy preload adjustment between adjacent first nut 21 and second nut 31 and enables cost reduction.

[0059] Third embodiment Next, a ball screw according to a third embodiment of the present invention will be described with reference to FIGS. Fig. 15 is a perspective view of a first nut 21E in a ball screw 11E according to a third embodiment of the present invention, viewed from the contact side. Fig. 16 is a side view of the contact side of the first nut 21E shown in Fig. 15. Fig. 17 is a cross-sectional view of the ball screw 11E according to the third embodiment, which corresponds to the VIII-VIII cross section in Fig. 1. Fig. 18 is a cross-sectional view for explaining the operation of the ball screw 11E according to the third embodiment shown in Fig. 17.

[0060] The ball screw 11E according to the third embodiment differs from the ball screw 11 of the first embodiment described above in that the through hole 25 is changed to a through hole 25E, and the predetermined distance between the pair of opposing walls 24a of the first slit 24 is made the same as the predetermined distance between the pair of opposing walls 34a of the second nut 31. Other configurations are substantially similar to those of the first embodiment described above, so the same reference numerals are used and detailed description will be omitted.

[0061] As shown in Fig. 15 and Fig. 16, the first nut 21E of the third embodiment has a through hole 25E penetrating between an axial end face 28a on the contact side and an axial end face 28b on the non-contact side. The through hole 25E is configured as a tapered hole, with an opening end 25a on the contact side of the first nut 21E opening in an arc shape extending in the circumferential direction and an opening end 25b on the non-contact side opening in a circular shape. Therefore, one end of the rotating shaft portion 43 rotatably supported in the through hole 25E is made displaceable in the circumferential direction along the opening end 25a.

[0062] In addition, since at least the opening end 25a on the abutment side of the through hole 25E is formed so as to expand in the circumferential direction, so that one end of the rotating shaft portion 43 can be displaced in the circumferential direction, the opening end 25a and the opening end 25b can also be configured as a straight hole having an opening cross-section that opens in an arc shape extending in the circumferential direction.

[0063] When the rotating shaft portion 43 is inserted into the through hole 25E and the annular convex portion 39 of the second nut 31 is fitted into the annular concave portion 29 of the first nut 21E, the preload applying portion 45 is disposed across the first slit 24 and the second slit 34. In other words, the preload applying portion 45 is disposed in the space defined by the first slit 24 and the second slit 34.

[0064] The predetermined distance between the pair of opposing walls 24a in the first nut 21E of this third embodiment is the same as the predetermined distance between the pair of opposing walls 34a of the second nut 31, as shown in Figure 17, and a gap is provided on both side walls of the preload applying portion 45 to allow it to swing.

[0065] Then, the preload adjusting part 41 is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43. Then, the preload applying part 45 presses one of the opposing walls 24a of the first slit 24 and one of the opposing walls 34a of the second slit 34, as shown in FIG. 18. At this time, the preload applying part 45 can be displaced in the circumferential direction along the arc-shaped opening end 25a, so that the first nut 21E and the second nut 31 can be rotated in opposite directions to each other, and the phases of the first nut 21E and the second nut 31 can be shifted. That is, the rotational torque of the rotating shaft part 43 is efficiently converted into a force that shifts the phases.

[0066] Therefore, in the ball screw 11E of the third embodiment, by rotating the preload adjustment part 41 in a clockwise direction, the preload applying part 45 simultaneously presses one of the opposing walls 24a in the first slit 24 and one of the opposing walls 34a in the second slit 34, and the force that shifts the phase of the first nut 21E and the second nut 31 applies a preload between the adjacent first nut 21E and second nut 31.

[0067] Therefore, according to the ball screw 11E of the third embodiment, like the ball screw 11 of the first embodiment described above, it is possible to provide a ball screw that allows for easy preload adjustment between the adjacent first nut 21E and second nut 31, thereby reducing costs.

[0068] (Fourth embodiment) Next, a ball screw according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 19 is a cross-sectional view of a ball screw 11F according to a fourth embodiment of the present invention, and corresponds to the cross section taken along line VIII-VIII in FIG.

[0069] The ball screw 11F according to the fourth embodiment differs from the ball screw 11E according to the third embodiment in that the first nut 21E and the second nut 31 are changed to a first nut 21F and a second nut 31F. Other configurations are substantially similar to those of the third embodiment, so the same reference numerals are used and detailed description is omitted.

[0070] As shown in FIG. 19, in a ball screw 11F, a first nut 21F and a second nut 31F are used instead of the first nut 21E and the second nut 31 of the third embodiment. In the first nut 21F, a pair of opposing walls 24a facing each other in the circumferential direction in the first slit 24F are not parallel, but are tapered surfaces that are inclined so that the distance between them increases toward the outer diameter direction. In the second nut 31F, a pair of opposing walls 34a facing each other in the circumferential direction in the second slit 34F are not parallel, but are tapered surfaces that are inclined so that the distance between them increases toward the inner diameter direction.

[0071] In the ball screw 11F according to the fourth embodiment, the preload adjusting part 41 is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43. Then, the preload applying part 45 presses one of the opposing walls 24a of the first slit 24F and one of the opposing walls 34a of the second slit 34F.

[0072] At this time, the preload applying portion 45 can be displaced in the circumferential direction along the arc-shaped opening end 25a, so that the first nut 21F and the second nut 31F can be rotated in opposite directions to each other, and the phases of the first nut 21F and the second nut 31F can be shifted. Furthermore, the preload applying portion 45 can efficiently apply pressure to the opposing walls 24a and 34a, which are tapered surfaces, because the pressing direction of the preload applying portion 45 is approximately perpendicular to the opposing walls 24a and 34a.

[0073] Therefore, according to the ball screw 11F of the fourth embodiment, like the ball screw 11E of the third embodiment described above, it is possible to provide a ball screw that allows for easy preload adjustment between the adjacent first nut 21F and second nut 31F and enables cost reduction.

[0074] Fifth embodiment Next, a ball screw according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 20 is a cross-sectional view of a ball screw 11G according to a fifth embodiment of the present invention, and corresponds to the cross section taken along line VIII-VIII in FIG.

[0075] The ball screw 11G according to the fifth embodiment differs from the ball screw 11E according to the third embodiment in that the first nut 21E and the second nut 31 are changed to a first nut 21G and a second nut 31G. The rest of the configuration is substantially the same as that of the third embodiment, so the same reference numerals are used and detailed description is omitted.

[0076] As shown in FIG. 20, in a ball screw 11G, a first nut 21G and a second nut 31G are used instead of the first nut 21E and the second nut 31 of the third embodiment. In the first nut 21G, a pair of opposing walls 24a opposing in the circumferential direction in the first slit 24G is not flat, but is a semi-cylindrical surface extending in the axial direction. In the second nut 31G, a pair of opposing walls 34a opposing in the circumferential direction in the second slit 34G is not flat, but is a semi-cylindrical surface extending in the axial direction.

[0077] In the ball screw 11G according to the fifth embodiment, the preload adjusting part 41 is rotated clockwise by a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft part 43. Then, the preload applying part 45 presses one of the opposing walls 24a of the first slit 24G and one of the opposing walls 34a of the second slit 34G.

[0078] At this time, the preload applying portion 45 can be displaced in the circumferential direction along the arc-shaped opening end 25a, so that the first nut 21G and the second nut 31G can be rotated in opposite directions to each other, and the phases of the first nut 21G and the second nut 31G can be shifted. Furthermore, the preload applying portion 45 can be smoothly pressed because it abuts against the opposing walls 24a and 34a, which are semi-cylindrical surfaces.

[0079] Therefore, according to the ball screw 11G of the fifth embodiment, like the ball screw 11E of the third embodiment described above, it is possible to provide a ball screw that allows for easy preload adjustment between adjacent first nut 21G and second nut 31G and enables cost reduction.

[0080] Sixth embodiment Next, a ball screw according to a sixth embodiment of the present invention will be described with reference to FIGS. Fig. 21 is an exploded perspective view of a ball screw 11H according to a sixth embodiment of the present invention. Fig. 22 is a side view of the contact side of the first nut 21H shown in Fig. 21, and Fig. 23 is a side view of the contact side of the second nut 31H. Fig. 24 is a cross-sectional view of the ball screw 11H according to the sixth embodiment, which corresponds to the VIII-VIII cross section in Fig. 1.

[0081] The ball screw 11H according to the sixth embodiment differs from the ball screw 11D according to the second embodiment in that a circular recess 40 is formed on an axial end face 38a on the contact side of a second nut 31H as one nut, and a circular protrusion 30 is formed on an axial end face 28a on the contact side of a first nut 21H as the other nut. Since the other configurations are substantially similar to those of the second embodiment described above, the same reference numerals are used and detailed description will be omitted.

[0082] In the ball screw 11H according to the sixth embodiment, as shown in Fig. 21 and Fig. 22, an annular convex portion 30 is formed on an axial end face 28a on the contact side of a first nut 21H serving as the other nut. A first slit 24A serving as the other slit that opens along the radial direction is cut out in a part of the annular convex portion 30. The first slit 24A has a pair of opposing walls 24a that face each other in the circumferential direction at a predetermined interval, and a bottom surface between the pair of opposing walls 24a is continuous with the axial end face 28a on the contact side.

[0083] Further, the through hole 25 formed in the first nut 21H has a through position displaced toward the inner circumference of the cylinder 22, and an opening end 25a at the axial end face 28a on the contact side opens into the bottom face of the first slit 24A.

[0084] As shown in Figs. 21 and 23, an annular recess 40 that is rotatably fitted onto the annular protrusion 30 is formed on an axial end face 38a on the contact side of a second nut 31H serving as one nut. A second slit 34A is formed by cutting out a part of the annular recess 40 as the other slit that opens so as to communicate with the first slit 24A along the same radial direction when the annular recess 40 is fitted onto the annular protrusion 30. The second slit 34A has a pair of opposing walls 34a that face each other in the circumferential direction at a predetermined interval, and the bottom surface between the pair of opposing walls 34a is continuous with the bottom surface of the annular recess 40.

[0085] Furthermore, a screw hole 36 is drilled in the annular recess 40 of the second nut 31H at a position symmetrical to the second slit 34A across the central axis of the nut. The screw hole 36 extends parallel to the central axis of the nut, and when the annular recess 40 is fitted onto the annular protrusion 30, an opening end of the screw hole 36 faces the bolt through hole 26 of the first nut 21H.

[0086] The second nut 31H, in which the annular recess 40 is rotatably fitted onto the annular protrusion 30 of the first nut 21H, is positioned adjacent to the first nut 21H on the opposite side of the flange portion 23 of the first nut 21H and rotatably relative to the first nut 21H around the central axis.

[0087] When the rotating shaft portion 43 is inserted into the through hole 25 and the annular recess 40 of the second nut 31H is fitted into the annular protrusion 30 of the first nut 21H, the preload applying portion 45D is disposed across the first slit 24A and the second slit 34A, as shown in Fig. 24. That is, the preload applying portion 45D is disposed in the space defined by the first slit 24A and the second slit 34A.

[0088] In the sixth embodiment, the predetermined distance between the pair of opposing walls 24a of the first nut 21H is wider than the predetermined distance between the pair of opposing walls 34a of the second nut 31H. The pair of opposing walls 34a of the second nut 31H are in close proximity to both side walls of the preload applying portion 45D with almost no gap between them. In contrast, the pair of opposing walls 24a of the first nut 21H are in a state in which there is a gap between them that allows them to swing relative to both side walls of the preload applying portion 45D.

[0089] Therefore, when the preload adjustment part 41D is rotated counterclockwise using a hexagonal wrench or the like fitted into the hexagonal hole 47 of the rotating shaft portion 43, the preload application portion 45D presses one of the opposing walls 34a in the second slit 34A, and the phase of the second nut 31H can be shifted in the R direction around the axis relative to the first nut 21H.

[0090] At this time, the lead direction of the first nut 21H and the second nut 31H is set so that the direction in which the second nut 31H is displaced in the R direction relative to the first nut 21H is the direction in which preload is applied. Therefore, when the preload-adjusting part 41D is rotated in the counterclockwise direction, preload is applied, and when the preload-adjusting part 41D is rotated in the clockwise direction, the preload is released.

[0091] In other words, in the ball screw 11H of the sixth embodiment, by rotating the preload adjustment part 41D counterclockwise, the preload application part 45D presses one of the opposing walls 34a in the second slit 34A, and a preload can be applied between the adjacent first nut 21H and second nut 31H by a force that shifts the phase of the second nut 31H in the R direction around the axis relative to the first nut 21H.

[0092] Therefore, according to the ball screw 11H of the sixth embodiment, like the ball screw 11D of the second embodiment described above, it is possible to provide a ball screw that allows for easy preload adjustment between adjacent first nut 21H and second nut 31H and enables cost reduction.

[0093] The present invention is not limited to the above-described embodiment, and can be appropriately modified, improved, etc. In addition, the material, shape, size, number, arrangement location, etc. of each component in the above-described embodiment are arbitrary as long as the present invention can be achieved, and are not limited.

[0094] For example, the preload adjustment part and the nut fixing bolt are not limited to being configured to be rotated from the axial end face side of the non-contact side of one nut, but can also be configured to be rotated from the axial end face side of the non-contact side of the other nut, and the preload adjustment part and the nut fixing bolt may be provided separately on one nut or the other nut, respectively. It is also possible to provide a plurality of first slits, a plurality of second slits, a plurality of preload adjusting parts, and a plurality of nut fixing bolts, thereby making the ball screw equipped with a plurality of preload adjusting mechanisms.

[0095] Here, the features of the above-mentioned embodiments of the ball screw according to the present invention will be briefly summarized and listed in the following [1] to [4].

[0096] [1] A screw shaft (13) having a spiral screw shaft side raceway groove (14) formed on an outer circumferential surface thereof; two nuts (21, 31; 31H, 21H) each having a spiral nut-side raceway groove (27, 37) formed on its inner circumferential surface so as to face the screw-shaft-side raceway groove (14) and fitted onto the screw shaft (13) so as to abut against each other; a plurality of balls (61) rolling in a ball rolling path formed by the nut side raceway grooves (27, 37) and the screw shaft side raceway groove (14) in each of the two nuts (21, 31; 31H, 21H); a preload adjustment mechanism (1; 1H) provided between the two nuts (21, 31; 31H, 21H); A ball screw (11, 11A to 11H) comprising: The preload adjustment mechanism (1;1H) is An annular recess (29; 40) formed on an axial end surface (28a) of the contact side of one nut (the first nut 21; the second nut 31H) of the two nuts (21, 31; 31H, 21H), An annular convex portion (39; 30) is formed on an axial end surface (38a) of the contact side of the other nut (the second nut 31, the first nut 21H) of the two nuts (21, 31; 31H, 21H) and is rotatably fitted into the annular concave portion (29; 40); One of the slits (first slit 24; second slit 34A) formed in the outer peripheral wall of the annular recess (29; 40) along the radial direction, The other slit (second slit 34; first slit 24A) is formed in the annular convex portion (39; 30) so as to communicate with the one slit (first slit 24; second slit 34A) along the same radial direction, a through hole (25, 25E) formed between the axial end face (28a; 38a) on the contact side and the axial end face (28b; 38b) on the non-contact side of the one nut (first nut 21; second nut 31H) or the other nut (second nut 31; first nut 21H) and communicating with at least one of the one slits (first slit 24; second slit 34A) and the other slit (second slit 34; first slit 24A); a preload adjusting component (41, 41A to 41D) including a preload applying portion (45, 45D) arranged across the one slit (first slit 24; second slit 34A) and the other slit (second slit 34; first slit 24A), and a rotating shaft portion (43) rotatably passing through the through hole (25, 25E) and for applying a rotational force to the preload applying portion (45, 45D) provided at one end; a nut fixing bolt (51) having a threaded portion (53) passing through a bolt through hole (26) provided in either one of the one nut (first nut 21; second nut 31H) or the other nut (second nut 31; first nut 21H) from the axial end face (28b; 38b) side of the non-contact side, the threaded portion (53) being screwed into either the other other nut (second nut 31; first nut 21H) or the one nut (first nut 21; second nut 31H), thereby fixing the one nut (first nut 21; second nut 31H) and the other nut (second nut 31; first nut 21H) so as not to rotate relative to each other; A ball screw (11, 11A to 11H) comprising:

[0097] According to the ball screw (11, 11A to 11H) having the configuration [1] above, the preload can be adjusted by rotating the preload adjustment part (41, 41A to 41D) to shift the phase between one adjacent nut (first nut 21; second nut 31H) and the other adjacent nut (second nut 31; first nut 21H), thereby making it possible to adjust the preload without using a spacer. That is, the ball screw (11, 11A to 11H) does not require thickness adjustment (grinding) of the spacer, which allows for cost reduction. Furthermore, the ball screw (11, 11A to 11H) can apply and release preload by changing the rotation direction of the preload adjustment part (41, 41D), making the assembly work easy. Moreover, the ball screw (11, 11A to 11H) of this configuration has a fitting structure in which the annular convex portion (39; 30) of the other nut (second nut 31; first nut 21H) is fitted into the annular concave portion (29; 40) of one nut (first nut 21; second nut 31H). Therefore, the ball screw (11, 11A to 11H) of the double nut type suppresses nut outer diameter runout, and does not require adjustment work. In addition, in the ball screw (11, 11A to 11H) of this configuration, the preload can be adjusted by turning the preload adjustment part (41, 41A to 41D) from the non-contact side of one nut (first nut 21; second nut 31H), and then the one nut (first nut 21; second nut 31H) and the other nut (second nut 31; first nut 21H) can be bolted together by the nut fixing bolt (51) so as not to rotate relative to each other. Thus, even when the ball screw (11, 11A to 11H) is attached to a machine, the preload can be adjusted without removing the one nut (first nut 21; second nut 31H) and the other nut (second nut 31; first nut 21H) from the bracket.

[0098] [2] The preload applying portion (45D) of the preload adjusting part (41D) is formed in a substantially rectangular parallelepiped shape with an outer peripheral surface along a rotational direction being chamfered, One end of the rotating shaft portion (43) is connected to one longitudinal end of the preload applying portion (45D). The ball screw (11D) according to the above [1].

[0099] According to the ball screw (11D) having the configuration [2] above, when the rotating shaft portion (43) is rotated, the preload applying portion (45D) has a rotation center at one end in the longitudinal direction, and the rotation radius of the other end in the longitudinal direction, which is the swing end, can be increased. Therefore, the preload adjusting part (41D) can shift the phase between one nut (first nut 21; second nut 31H) and the other nut (second nut 31; first nut 21H) by a larger rotation radius due to the swing end of the preload applying portion (45D). [3] At least the opening end (25a) on the contact side of the through hole (25E) is formed to expand in the circumferential direction, so that one end of the rotating shaft portion (43) is displaceable in the circumferential direction. The ball screw (11E) according to the above [1].

[0100] According to the ball screw (11E) having the configuration [3] above, when the rotating shaft portion (43) of the preload adjusting part (41) is rotated, the preload applying portion (45) can be displaced in the circumferential direction along the opening end 25a formed to expand in the circumferential direction. Thus, one nut (first nut 21E) and the other nut (second nut 31) can be rotated in the opposite directions to each other, and the phase of the one nut (first nut 21E) and the other nut (second nut 31) can be shifted. That is, the rotational torque of the rotating shaft portion is efficiently converted into a force that shifts the phase.

[0101] [4] The through hole (25, 25E) and the bolt through hole (26) are provided in either the one nut (first nut 21; second nut 31H) or the other nut (second nut 31; first nut 21H), The ball screw (11, 11A to 11H) according to any one of the above items [1] to [3].

[0102] According to the ball screw (11, 11A to 11H) having the configuration [4] above, the preload adjustment part (41, 41A to 41D) and the nut fixing bolt (51) can be rotated from the axial end face (28b) on the same non-contact side, improving the workability of preload adjustment. [Explanation of symbols]

[0103] 1 Preload adjustment mechanism 11 Ball screw 13 Screw shaft 14 Screw shaft side raceway groove 21 First nut (one of the nuts) 24 First slit (one of the slits) 27 Nut side raceway groove 28a Axial end face of the abutting side 28b Axial end face on the non-contact side 29 Circular recess 31 Second nut (the other nut) 34 Second slit (the other slit) 37 Nut side raceway groove 39 Circular convex part 41 Preload adjustment parts 43 Rotating shaft 45 Preloading section 51 Nut fixing bolt 53 Screw part 61 Ball

Claims

1. a screw shaft having a spiral screw shaft side raceway groove formed on an outer circumferential surface; two nuts each having a spiral nut-side raceway groove formed on an inner peripheral surface thereof so as to face the screw-shaft-side raceway groove, and each being fitted around the screw shaft and abutting against each other; a plurality of balls rolling in a ball rolling path formed by the nut side raceway groove and the screw shaft side raceway groove of each of the two nuts; a preload adjustment mechanism provided between the two nuts; A ball screw comprising: The preload adjustment mechanism includes: An annular recess formed on an axial end surface of one of the two nuts on a contact side; an annular protrusion formed on an axial end surface of the other nut on the contact side of the other of the two nuts and rotatably fitted into the annular recess; One slit formed in an outer peripheral wall of the annular recess along a radial direction; Another slit is formed in the annular convex portion so as to communicate with the one slit along the same radial direction; and a through hole formed between the axial end surface of the abutment side and the axial end surface of the non-abutment side in the one nut or the other nut, and communicating with at least one of the one slits and the other slit; a preload adjusting component including a preload applying portion disposed across the one slit and the other slit, and a rotating shaft portion rotatably passing through the through hole and provided at one end thereof for applying a rotational force to the preload applying portion; a nut fixing bolt having a threaded portion passing through a bolt through hole provided in either the one nut or the other nut from an axial end face side on the opposite contact side and screwed into either the other nut or the one nut, thereby fixing the one nut and the other nut so that they cannot rotate relative to each other; A ball screw comprising:

2. The preload applying portion of the preload adjusting component is formed in a substantially rectangular parallelepiped shape with an outer circumferential surface along a rotational direction being chamfered, One end of the rotating shaft portion is connected to one longitudinal end of the preload applying portion.

2. The ball screw according to claim 1 .

3. The through hole is opened such that at least an opening end on the abutment side is opened in an elliptical shape extending in the circumferential direction.

2. The ball screw according to claim 1 .

4. The through hole and the bolt through hole are provided in either the one nut or the other nut.

4. The ball screw according to claim 1, wherein the ball screw is a ball bearing.

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