Ball screw device

Abstract

To provide a ball screw device capable of easily taking out and favorably and smoothly operating balls in outside a circulation path formed by a circulating piece while suppressing cost.SOLUTION: A ball screw device is equipped with a screw shaft 10 that has a spiral first screw groove 11 on an outer peripheral surface, a nut 20 that has a spiral second screw groove 21 on an inner peripheral surface and is externally fitted with the screw shaft 10, a plurality of balls 30 that is stored in a rolling path 32 formed by the first screw groove 11 of the screw shaft 10 and the second screw groove 21 of the nut 20, and a circulating piece 40 that is fitted in an attaching hole 27 formed on the nut 20 and has a ball returning passage 42 forming a circulating path 34 that connects a rolling path 32 and allows the balls 30 to circulate for each lead. The circulating piece 40 has a through-hole 44 into which the ball 30 can be inserted, and the through-hole 44 is communicated with a place different from a place configuring the circulating path 34 in the rolling path 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A ball screw device is a device in which balls are inserted into screw grooves provided on the screw shaft and nut, and when the screw shaft or nut rotates, the balls rotate and revolve, thereby converting rotational motion into linear motion with high efficiency.

[0003] This ball screw device is designed so that the balls are always present and circulating within a circulation path (circuit), which is the groove in which the balls revolve, so that the screw shaft or nut can continuously convert rotational motion into linear motion.There are various circulation methods for circulating the balls, such as the tube type, top type, and end cap type.

[0004] In the ball screw circulation system, which is one of the circulation systems used in ball screw devices, the assembly process generally involves passing a cylindrical temporary shaft through a nut equipped with a circulation top having a ball return passage, inserting a specified number of balls into the circulation passage, and then transferring the temporary shaft to the screw shaft, which is the main shaft with a threaded groove.

[0005] However, if the balls are accidentally inserted into a thread groove outside the circulation path during the ball insertion process, the balls will not circulate smoothly after being transferred to the screw shaft. This can cause a locking phenomenon in which the rotational motion of the nut and screw shaft is not smoothly converted into linear motion, preventing the nut and screw shaft from rotating.

[0006] Patent document 1 shows a ball screw device having a plurality of balls circulating in a circulation path, in which a ball removal hole with a diameter larger than the ball diameter is provided in a screw groove outside the circulation path, and the balls outside the circulation path can be removed from this ball removal hole.

[0007] Furthermore, Patent Document 2 discloses a ball screw device in which a circulation groove is formed in a ball guide member that closes a through hole formed in a nut, and the ball guide member has a ball insertion hole that is closed by a fitting portion of a ball insertion hole closing member. In this ball screw device, when a ball is inserted through the ball insertion hole of the ball guide member, the ball is prevented from coming off to an unexpected position. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Jikko No. 48-27326 [Patent Document 2] Japanese Patent Application Publication No. 7-174205 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the ball screw device described in Patent Document 1, the ball removal holes are drilled in the nut itself, which increases the number of processing steps and leads to increased costs. Also, nuts are generally heat-treated, so it is necessary to consider the effects of thermal deformation, making it unrealistic to drill ball removal holes in the nut.

[0010] In addition, in the ball screw device described in Patent Document 2, the balls are inserted through the ball insertion holes of the ball guide members that make up the circulating top, preventing the balls from falling off to positions outside the circulating path; however, this increases the number of parts in the circulating top, resulting in increased costs.

[0011] Therefore, an object of the present invention is to provide a ball screw device that can easily remove balls that have fallen outside the circulation path formed by the circulation top and operate well and smoothly while keeping costs down. [Means for solving the problem]

[0012] The present invention comprises the following configurations. a screw shaft having a spiral thread groove on its outer circumferential surface; A nut having a spiral thread groove on its inner peripheral surface and fitted onto the screw shaft; a plurality of balls accommodated in rolling paths formed by the screw shaft and the screw grooves of the nut; a circulation top having a ball return passage that is fitted into a mounting hole formed in the nut and connects the rolling paths to form a circulation path through which the balls can circulate for each lead; Equipped with The circulating top has a through hole through which the ball can be inserted, The through hole communicates with a location in the rolling path that is different from a location that forms the circulation path. Ball screw device. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a ball screw device that can easily remove balls that have fallen outside the circulation path formed by the circulation top and operate the balls well and smoothly while keeping costs down. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view of a ball screw device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of a nut constituting the ball screw device according to the embodiment, cut away in the axial direction. [Figure 3] FIG. 10 is a perspective view of a circulating top attached to a nut. [Figure 4A] This is a plan view of the circulation top viewed from the opposite side to the side where it is attached to the nut. [Figure 4B] FIG. [Figure 4C] FIG. 10 is a plan view of the circulation top as seen from the attachment side to the nut. [Figure 5] FIG. 1 is a perspective view of a ball screw device equipped with a sealing member. [Figure 6] FIG. 10 is a perspective view of a nut constituting a ball screw device according to a modified example, cut away in the axial direction. [Figure 7A] This is a plan view seen from the opposite side to the side where the circulation top is attached to the nut. [Figure 7B] FIG. [Figure 7C] FIG. 10 is a plan view of the circulation top as seen from the attachment side to the nut. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a perspective view of a ball screw device 100 according to this embodiment. Fig. 2 is a perspective view of a nut 20 constituting the ball screw device 100 according to this embodiment, cut away in the axial direction.

[0016] 1 and 2, a ball screw device 100 according to this embodiment includes a screw shaft 10, a nut 20, a plurality of balls 30, and a plurality of circulation tops 40 serving as a circulation section. The screw shaft 10 is formed to have a circular cross section, and has a first spiral screw groove (thread groove) 11 formed on its outer circumferential surface.

[0017] The nut 20 is generally cylindrical, with an inner diameter larger than the outer diameter of the screw shaft 10, and is fitted onto the screw shaft 10 with a predetermined gap. One end of the nut 20 is provided with a flange 25 for coupling to a guide object. The flange 25 has a plurality of bolt holes 26. The nut 20 is fixed to the guide object by fastening bolts (not shown) inserted through these bolt holes 26 to the guide object. The inner peripheral surface of the nut 20 is formed with a second screw groove (thread groove) 21 having the same lead as the first screw groove 11 of the screw shaft 10 and facing the first screw groove 11. The first screw groove 11 of the screw shaft 10 and the second screw groove 21 of the nut 20 form a rolling path 32 with a generally circular cross section, and a plurality of balls 30 are filled and arranged in this rolling path 32 so as to be able to roll.

[0018] A circulation top 40 is attached to the nut 20 to return the balls 30 to the preceding rolling path 32. A ball return passage 42 is formed in the circulation top 40, connecting one end of the rolling path 32 with the other end of the rolling path 32 one lead before. This ball return passage 42 scoops up the balls 30 rolling along the rolling path 32 toward each circulation top 40 in the radial direction of the screw shaft 10, and then causes them to ride over the threads of the screw shaft 10 and return to the rolling path 32 one lead before, allowing the balls 30 to circulate.

[0019] The ball return passage 42 and the rolling path 32 form an infinite circulation path 34 (hereinafter simply referred to as the circulation path) that is called a substantially annular circuit on the outside of the screw shaft 10. As a result, as the screw shaft 10 rotates relative to the nut 20, the plurality of balls 30 circulate infinitely within the circulation path 34, allowing the screw shaft 10 and the nut 20 to move linearly relative to each other in the axial direction.

[0020] The nut 20 has a mounting hole 27 formed therethrough from the front to the back. The mounting hole 27 is formed in a circular shape, and a circulation top 40 is attached to the mounting hole 27. The outer peripheral surface of the nut 20 has a pair of engagement grooves 28 that connect to the mounting hole 27. The pair of engagement grooves 28 are formed in opposing positions with the mounting hole 27 in between.

[0021] Fig. 3 is a perspective view of the circulating top 40 attached to the nut 20. Fig. 4A is a plan view of the circulating top 40 viewed from the side opposite to the side attached to the nut 20. Fig. 4B is a side view of the circulating top 40. Fig. 4C is a plan view of the circulating top 40 viewed from the side attached to the nut 20.

[0022] As shown in Figures 3, 4A, 4B, and 4C, the circulation top 40 has a circular cross section, and a ball return passage 42 is formed in an end face 40a on the front side in the fitting direction into the mounting hole 27 of the nut 20. The circulation top 40 also has a pair of through holes 44. The pair of through holes 44 are formed at positions on either side of the ball return passage 42 in the circulation top 40. The pair of through holes 44 extend along the axial direction and pass through the circulation top 40. The pair of through holes 44 have an inner diameter slightly larger than the outer diameter of the balls 30, allowing the balls 30 to pass through.

[0023] The circulation top 40 also has a pair of introduction grooves 45. The pair of introduction grooves 45 are connected to the through-hole 44 from the outer periphery of the end face 40a of the circulation top 40, and extend in opposite directions. The circulation top 40 also has a pair of overhanging portions 46 at the end on the rear side in the fitting direction of the nut 20 into the mounting hole 27. The pair of overhanging portions 46 extend in opposite directions.

[0024] The circulation top 40 is fitted into the mounting hole 27 from the outer periphery of the nut 20. At this time, the pair of protrusions 46 of the circulation top 40 are fitted into the pair of engaging grooves 28 formed on the outer periphery of the nut 20. As a result, the circulation top 40 is attached to the nut 20 in a state where it is prevented from rotating, and the end face 40a where the ball return passage 42 is formed is positioned at the position of the inner periphery of the nut 20.

[0025] When the circulating top 40 is attached to the nut 20 in this manner, one end of the second screw groove 21 forming the rolling path 32 is connected by the ball return passage 42 to the other end of the second screw groove 21 forming the rolling path 32 one lead before, as shown in Figure 2. In addition, the pair of introduction grooves 45 of the circulating top 40 are connected to the second screw grooves 21 adjacent to both sides of the second screw grooves 21 connected by the ball return passage 42. As a result, the pair of through holes 44 of the circulating top 40 are connected via the pair of introduction grooves 45 to the second screw grooves 21 adjacent to both sides of the second screw groove 21 connected by the ball return passage 42.

[0026] In the ball screw device 100 configured as described above, for example, a cylindrical temporary shaft is passed through the nut 20 to which the circulating top 40 is attached, and a specified number of balls 30 are inserted into the second screw groove 21 that serves as the circulation path 34 in the nut 20, and then the temporary shaft is transferred to the screw shaft 10. This results in the ball screw device 100 having the specified number of balls 30 circulatably arranged in the circulation path 34 consisting of the first screw groove 11 of the screw shaft 10 and the second screw groove 21 of the nut 20.

[0027] In the ball screw device 100 configured in this manner, the introduction groove 45 of the circulation top 40 is connected to a location in the rolling path 32 different from the location that forms the circulation path 34, and the through hole 44 is communicated.

[0028] Incidentally, when inserting the balls 30, the balls 30 may accidentally enter the rolling paths 32 outside the circulation path 34. In this case, in the ball screw device 100, when the screw shaft 10 and the nut 20 are rotated relative to each other, the balls 30 that have entered the rolling paths 32 outside the circulation path 34 roll along the rolling paths 32 and are guided to the through holes 44 by the guide grooves 45 of the circulation top 40. Then, the balls 30 that have been guided to the through holes 44 are discharged to the outside through the through holes 44.

[0029] As described above, in the ball screw device 100 according to this embodiment, when the screw shaft 10 and the nut 20 are rotated relative to each other, the balls 30 that are present outside the circulation path 34 in the rolling path 32 are guided to the through hole 44 of the circulation top 40 and are discharged to the outside through this through hole 44. As a result, the balls 30 that have entered outside the circulation path 34 in the rolling path 32 can be easily removed simply by attaching the circulation top 40 to the nut 20 without changing the shape or structure of the nut 20, and a high-quality ball screw device 100 can be obtained in which the nut 20 and the screw shaft 10 can rotate smoothly. In addition, the through hole 44 can be used as a filling hole for lubricating oil for the rolling path 32.

[0030] Moreover, the circulation top 40 has an introduction groove 45 that guides balls 30 at a location in the rolling path 32 other than the location that forms the circulation path 34 to the through hole 44. This allows balls 30 that are present outside the circulation path 34 in the rolling path 32 to be smoothly guided by the introduction groove 45 to the through hole 44 and discharged.

[0031] 5, the circulating top 40 of the ball screw device 100 preferably includes a sealing member 47 that fits into the through hole 44. The sealing member 47 is made of an elastic material such as resin, and seals the through hole 44 by fitting into it.

[0032] In this way, by providing the sealing member 47 that seals the through hole 44 of the circulating top 40, the through hole 44 can be closed by the sealing member 47 after the balls 30 are discharged from the circulating path 34 in the rolling path 32. This makes it possible to prevent foreign matter such as dust from entering the rolling path 32 from the through hole 44, and maintain smooth rotational movement between the nut 20 and the screw shaft 10.

[0033] Next, a modified example will be described. The same components as those in the above embodiment are denoted by the same reference numerals and the description thereof will be omitted. Fig. 6 is a perspective view of the nut 20 constituting the ball screw device according to the modified example, broken away in the axial direction. Fig. 7A is a plan view of the circulating top 40 as seen from the side opposite to the attachment side to the nut 20. Fig. 7B is a side view of the circulating top 40. Fig. 7C is a plan view of the circulating top 40 as seen from the attachment side to the nut 20.

[0034] 6, 7A, 7B, and 7C, in this modification, an oval mounting hole 27A is formed in the nut 20, and a circulating top 40A having an oval cross section is fitted into this mounting hole 27A. By fitting the circulating top 40A into this mounting hole 27A, the circulating top 40A can be easily attached to the nut 20 in a state where it is prevented from rotating.

[0035] In addition, the shape of the mounting hole 27A and the circulation top 40A may be elliptical, and in this case, by fitting the circulation top 40A into the mounting hole 27A, the circulation top 40A can be easily attached to the nut 20 in a state where it is prevented from rotating.

[0036] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0037] As described above, the present specification discloses the following: (1) a screw shaft having a helical thread groove on its outer circumferential surface; A nut having a spiral thread groove on its inner peripheral surface and fitted onto the screw shaft; a plurality of balls accommodated in rolling paths formed by the screw shaft and the screw grooves of the nut; a circulation top having a ball return passage that is fitted into a mounting hole formed in the nut and connects the rolling paths to form a circulation path through which the balls can circulate for each lead; Equipped with The circulating top has a through hole through which the ball can be inserted, The through hole communicates with a location in the rolling path that is different from a location that constitutes the circulation path. In this ball screw device, when the screw shaft and the nut are rotated relative to each other, balls that are outside the circulation path in the rolling path are guided into the through hole of the circulation top and discharged to the outside through this through hole. This allows balls that have entered outside the circulation path in the rolling path to be easily removed simply by attaching the circulation top to the nut without changing the shape or structure of the nut, resulting in a high-quality ball screw device that allows smooth rotation of the nut and screw shaft. The through hole can also be used as a filling hole for lubricating oil into the rolling path.

[0038] (2) The ball screw device according to (1), wherein the circulation top has an introduction groove that guides the balls at a location in the rolling path different from the location that constitutes the circulation path to the through hole. According to this ball screw device, balls present outside the circulation path in the rolling path can be smoothly guided to the through hole by the introduction groove and discharged.

[0039] (3) The ball screw device according to (1) or (2), wherein the circulation top is provided with a sealing member that fits into the through hole and seals the through hole. According to this ball screw device, by sealing the through hole with a sealing member after the balls are discharged from the circulation path in the rolling path, it is possible to prevent foreign matter such as dust from entering the rolling path from the through hole, thereby maintaining smooth rotational movement of the nut and the screw shaft.

[0040] (4) The ball screw device according to any one of (1) to (3), wherein the cross-sectional shapes of the mounting hole of the nut and the circulation top are formed in an oval shape or an elliptical shape. According to this ball screw device, by fitting the circulation top into the mounting hole, the circulation top can be easily mounted in a state where it is prevented from rotating relative to the nut. [Explanation of symbols]

[0041] 10 Screw shaft 11 First screw groove (screw groove) 20 nuts 21 Second screw groove (screw groove) 27 mounting holes 30 balls 32 Rolling path 34 Circulation path 40 Circulation Top 42 Ball return passage 44 through holes 45 Introduction groove 47 Sealing member

Claims

1. a screw shaft having a spiral thread groove on its outer circumferential surface; A nut having a spiral thread groove on its inner peripheral surface and fitted onto the screw shaft; a plurality of balls accommodated in rolling paths formed by the screw shaft and the screw grooves of the nut; a circulation top having a ball return passage that is fitted into a mounting hole formed in the nut and connects the rolling paths to form a circulation path through which the balls can circulate for each lead; Equipped with The circulating top has a through hole through which the ball can be inserted, The through hole communicates with a location in the rolling path that is different from a location that forms the circulation path. Ball screw device.

2. The circulation top has an introduction groove that guides the balls at a location in the rolling path different from a location that constitutes the circulation path to the through hole. The ball screw device according to claim 1 .

3. The circulation top includes a sealing member that is fitted into the through hole and seals the through hole. The ball screw device according to claim 1 or 2.

4. The cross-sectional shape of the mounting hole of the nut and the cross-sectional shape of the circulation top are formed in an oval shape or an elliptical shape. The ball screw device according to any one of claims 1 to 3.

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