Ball screw

Abstract

A ball screw (10) comprises: a screw shaft (20) formed with a screw shaft-side raceway groove (21); a nut (30) formed with a nut-side raceway groove (31) and having a through-hole (32) communicating an outer peripheral surface (33) with the nut-side raceway groove (31); a plurality of balls (26) that roll on a load raceway (25); and a circulating part (40) that is attached to the through-hole (32) to form a ball returning path (48) for circulating the balls (26). The ball screw (10) has a sealing member (50) made of resin or rubber that seals at least a part of a gap between an inner peripheral surface of the through-hole (32) of the nut (30) and an outer peripheral surface of the circulating part (40). This makes it possible to prevent leakage of grease through the gap between the circulating part and the through-hole formed on the nut, and entry of external foreign matter through the gap.

Description

Technical Field

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[0001] The present invention relates to a ball screw, and particularly to a ball screw capable of preventing grease leakage from inside the nut and intrusion of foreign matter from outside.

Background Art

[0002] In recent years, ball screws for high-load driving having balls with a size of 0.5 to 1 inch have been used as a replacement for hydraulic drive mechanisms. On the other hand, in recent years, particularly in the injection shaft of an injection molding machine, there is a strong demand to improve the high-speed driving and heat resistance of the ball screw due to high cycling and high-speed injection molding.

[0003] Hitherto, in response to the demand for high-speed feed, it has been dealt with by a resin-made circulation component having a three-dimensional ball return passage capable of scooping up balls from the tangential direction of the load track. However, since the resin-made circulation component has limitations in terms of strength and heat resistance, in order to solve these problems, the circulation component has been made of a metal material.

[0004] Patent Documents 1 and 2 describe a method of manufacturing a U-shaped circulation component by press working. The U-shaped circulation component is stably attached with both ends inserted and fitted into circular holes provided in the nut. In particular, in Patent Document 2, an O-ring groove is formed in the circular hole, and the gap between the circulation component and the hole is sealed with an O-ring to prevent grease leakage from the gap.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in Patent Document 2, the gap between the circulating part and the hole is sealed with an O-ring to prevent grease leakage from the gap. However, this requires additional processing of the nut, such as machining an O-ring groove to fit the O-ring, which may increase costs.

[0007] Furthermore, if the scooping portion of the metal circulating component is formed along the tangential direction of the load track, the nut hole will no longer be circular. Also, due to the constraints of the shape, a suitable gap is required between the nut hole (through hole) and the circulating component. This gap may cause grease to leak and contaminate the surrounding area, or foreign matter to enter through the gap, potentially reducing the lifespan of the component.

[0008] The present invention has been made in view of the aforementioned problems, and its purpose is to provide a ball screw that can prevent grease from leaking out of the gap between the circulating part and the through hole formed in the nut, and prevent foreign matter from entering through the gap. [Means for solving the problem]

[0009] The above objective of the present invention is achieved by the following configuration. [1] A screw shaft having a helical screw shaft side raceway groove formed on its outer surface, A nut having a nut-side raceway groove formed on its inner circumferential surface opposite to the screw shaft-side raceway groove, and a through hole provided that connects the outer circumferential surface and the nut-side raceway groove, Multiple balls that roll along a load track formed by the screw shaft side track groove and the nut side track groove, A circulating component attached to the through hole forms a ball return passage for circulating the balls that roll along the load track, A ball screw equipped with, A ball screw comprising a resin or rubber sealing member that seals at least a portion of the gap between the inner circumferential surface of the through hole of the nut and the outer circumferential surface of the circulating component. [Effects of the Invention]

[0010] According to the ball screw of the present invention, it is possible to prevent grease from leaking out of the gap between the circulating component and the through hole formed in the nut, and to prevent foreign matter from entering through the gap. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a plan view of a ball screw according to the first embodiment of the present invention. [Figure 2] Figure 2 is an exploded perspective view of the ball screw shown in Figure 1. [Figure 3] Figure 3 is a perspective view of the sealing member shown in Figure 2. [Figure 4] Figure 4(a) is a top view of the sealing member shown in Figure 3, Figure 4(b) is a front view of the sealing member shown in Figure 3, Figure 4(c) is a bottom view of the sealing member shown in Figure 3, Figure 4(d) is a left side view of the sealing member shown in Figure 3, Figure 4(e) is a right side view of the sealing member shown in Figure 3, and Figure 4(f) is a rear view of the sealing member shown in Figure 3. [Figure 5] Figure 5 is a cross-sectional view showing the positional relationship between the load trajectory on which the ball rolls, the scooping section for the circulating component, and the through-hole of the nut. [Figure 6] Figure 6 is a plan view of a ball screw according to a second embodiment of the present invention. [Figure 7] Figure 7 is an exploded perspective view of the ball screw shown in Figure 6. [Figure 8] Figure 8 is a perspective view of the sealing member shown in Figure 7. [Figure 9] Figure 9(a) is a top view of the sealing member shown in Figure 8, Figure 9(b) is a front view of the sealing member shown in Figure 8, Figure 9(c) is a bottom view of the sealing member shown in Figure 8, Figure 9(d) is a left side view of the sealing member shown in Figure 8, Figure 9(e) is a right side view of the sealing member shown in Figure 8, and Figure 9(f) is a rear view of the sealing member shown in Figure 8. [Figure 10] Figure 10 is a perspective view of a sealing member according to a first modified example of a second embodiment, in which a pair of sealing members are integrally formed. [Figure 11]FIG. 11 is a perspective view of a sealing member according to a second modification of the second embodiment, which is formed of two parts each having a connecting portion. [Figure 12] FIG. 12(a) is a perspective view of a sealing member according to a third modification of the second embodiment, and FIG. 12(b) is a perspective view showing a state where the sealing member is assembled to a through-hole of a nut. [Figure 13] FIG. 13(a) is a perspective view of a sealing member according to a fourth modification of the second embodiment, and FIG. 13(b) is a perspective view showing a state where the sealing member is assembled to a through-hole of a nut. [Figure 14] FIG. 14(a) is a perspective view of a through-hole sealing member of a nut according to a fifth modification of the second embodiment, and FIG. 13(b) is a perspective view showing a state where the sealing member is assembled to a through-hole of a nut. [Figure 15] FIGS. 15(a) to (c) are perspective views of a sealing member according to a sixth modification of the second embodiment. [Figure 16] FIG. 16 is a view corresponding to FIG. 4(b) of a sealing member of a modification of the present invention, which is formed in a tapered shape whose diameter gradually increases from the lower part to the upper part on the side surface. [Figure 17] FIG. 17 is a cross-sectional view showing the positional relationship of the scooping portion of the circulating component, the load track, and the through-hole of the nut, which is different from the form of FIG. 5. [Figure 18] FIG. 18 is a perspective view showing a modification in which the shape of the through-hole of the nut is changed in the form shown in FIG. 17.

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, each embodiment of the ball screw according to the present invention will be described in detail based on the drawings.

[0013] (First Embodiment) First, the ball screw of the first embodiment will be described with reference to FIGS. 1 to 5. As shown in Figures 1 and 2, the ball screw 10 of this embodiment comprises a screw shaft 20 having a helical screw shaft-side raceway groove 21 formed on its outer circumference, a nut 30 having a helical nut-side raceway groove 31 (see Figure 5) on its inner circumference opposite to the screw shaft-side raceway groove 21 of the screw shaft 20, and a pair of through holes 32 communicating with the nut-side raceway groove 31 provided on its outer circumference 33, and a number of balls 26 interposed to roll in a load raceway 25 formed by the screw shaft-side raceway groove 21 of the screw shaft 20 and the nut-side raceway groove 31 of the nut 30. Furthermore, the ball screw 10 comprises a circulating component (return tube) 40 attached to the through hole 32 of the nut 30 and having a ball return passage 48 for circulating the balls 26 rolling in the load raceway 25, and a sealing member 50 that seals the gap between the through hole 32 of the nut 30 and the circulating component 40.

[0014] The ball screw 10 of this embodiment is configured to include three circulation components 40, but the number of circulation components 40 can be set to any number depending on the number of ball circulation passages.

[0015] A pair of through holes 32, formed by connecting the outer circumferential surface 33 of the nut 30 and the nut-side raceway groove 31, are into which the nut insertion portions 46, which are the ends of the circulating component 40, are inserted. The circulating component 40 is screw-fixed to the outer circumferential surface 33 of the nut 30 by set screws 44 inserted through the screw holes 43 of the flanged U-shaped fastener 42.

[0016] The circulating part 40 is formed by bending a pipe member and has a straight section parallel to the flat surface 33a formed on the outer circumferential surface 33 of the nut 30 when attached to the nut 30, and nut insertion sections 46 in which both ends of the straight section 45 are bent to form a U shape when viewed from the side, and are twisted in opposite directions to form a Z shape when viewed from above. A scooping section 47 (see Figure 5) is provided at the tip of each nut insertion section 46.

[0017] As a result, when the circulating component 40 is attached to the nut 30, each scooping portion 47 is formed in a direction aligned with the tangential direction of the load track 25. This allows the circulating component 40 to scoop up the balls 26 rolling along the load track 25 from the tangential direction of the load track 25 with the scooping portion 47 and form a ball return passage 48 that returns the balls to the other position on the load track 25.

[0018] The circulating component 40 may be formed by bending a pipe member, but is not limited to this; it may also be formed in a pipe shape by combining two parts that are divided along the central axis of the circulating component 40.

[0019] The sealing member 50 is a member that seals the gap between the through hole 32 of the nut 30 and the circulation component 40, and is made of an elastic material such as resin or rubber. As shown in Figures 3 and 4, the sealing member 50 has a substantially U-shaped outer surface 51 that conforms to the shape of the inner surface of the through hole 32 and a substantially C-shaped inner surface 52 that conforms to the shape of the outer surface of the circulation component 40.

[0020] Furthermore, as shown in Figures 4(b) and 5, the upper surface 53 and lower surface 54 of the sealing member 50 are formed in an arc shape so as to follow the outer circumferential surface 33 and inner circumferential surface of the nut 30 when it is attached to the through hole 32 of the nut 30. As a result, when the sealing member 50 is attached to the nut 30, it does not protrude from the outer circumferential surface 33 of the nut 30.

[0021] Then, as shown in Figure 5, the circulating component 40 is inserted through the through hole 32 with both nut insertion portions 46 facing tangentially to the load track 25, and then the sealing member 50 is attached from above to the gap between the through hole 32 of the nut 30 and the circulating component 40. This seals the gap between the through hole 32 and the circulating component 40, preventing grease leakage from inside the nut 30 and the intrusion of foreign matter from the outside.

[0022] In particular, the sealing member 50 of this embodiment seals the side with a larger gap between the through hole 32 and the circulation component 40 (the right side of the nut insertion portion 46 in Figure 5). The gap between the through hole 32 and the sealing member 50, and the gap between the sealing member 50 and the circulation component 40, should preferably be 0.1 mm or less to prevent grease leakage and the intrusion of foreign matter from the outside. Alternatively, at least a portion of the sealing member 50 may be formed slightly larger than the circulation component 40 and press-fitted into the circulation component 40.

[0023] The gap between the inner surface of the nut insertion portion 46 of the circulating component 40 (the left side of the nut insertion portion 46 in Figure 5) and the side of the through hole 32 does not need to be covered with the sealing member 50 if it is a predetermined gap, for example, 0.1 mm or less. However, the shape of the sealing member 50 may be modified to also cover the inside of the circulating component 40 (the left portion of the nut insertion portion 46 in Figure 5), or another sealing member may be placed.

[0024] Furthermore, since the sealing member 50 is made of an elastic material such as resin or rubber, it can easily absorb processing errors in the through hole 32 and dimensional errors in the press-formed circulating part 40, and can be installed in the through hole 32 without any gaps. In addition, when used at high temperatures, the thermal expansion of the resin or rubber further reduces the gap between the through hole 32 and the circulating part 40.

[0025] Furthermore, since the scooping section 47 is mounted facing tangentially to the load track 25, the balls 26 rolling along the load track 25 can be smoothly introduced into the ball return passage 48, enabling high-speed feeding by allowing it to operate at high speed without any problems.

[0026] Furthermore, by making both the nut 30 and the circulation component 40 from metal, heat resistance is improved, which in turn allows for an increase in the driving speed of the ball screw 10.

[0027] (Second Embodiment) Next, a ball screw according to a second embodiment of the present invention will be described with reference to Figures 6 to 9. The ball screw of this embodiment differs from that of the first embodiment in that the shape of the sealing member differs from that of the first embodiment, and furthermore, the sealing member and the circulating component are simultaneously fixed to the nut by a cap member. In the following description, the same reference numerals or equivalent numerals are used for parts that are the same as in the first embodiment, and the description is simplified or omitted.

[0028] As shown in Figures 8 and 9, in this embodiment, the sealing member 50 has a substantially semicircular protrusion 55 that protrudes outward from the main body portion 70 below the portion along the upper surface 53 of the sealing member 50, relative to the main body portion 70 that fits into the through hole 32 of the nut 30. Furthermore, contact portions 56a and 56b that abut against the cap member 60 are formed on the side and top surfaces of the substantially semicircular protrusion 55, and a recess 57 that covers the bent portion 49 between the straight portion 45 and the nut insertion portion 46 of the circulating part 40 is provided on the back surface of the protrusion 55.

[0029] The cap member 60 includes a groove (not shown) with a substantially U-shaped cross-section that covers the straight portion 45 of the circulation component 40 and the bent portions 49 on both sides of the straight portion 45 in the longitudinal direction, and a flange portion 61 in which two screw holes 43 are formed.

[0030] After the circulating component 40 is formed in this manner, both nut insertion portions 46 are inserted into their respective through holes 32 in the tangential direction of the load track 25, and then a sealing member 50 is attached from above to the gap between the through hole 32 of the nut 30 and the circulating component 40. At this time, the bent portion 49 of the circulating component 40 is attached so as to be covered by the recess 57 of the sealing member 50.

[0031] Next, as shown in Figures 6 and 7, the cap member 60 is placed over the circulation component 40 and the sealing member 50, and is fixed to the outer surface 33 of the nut 30 by a set screw 44 inserted through the screw hole 43. At this time, the cap member 60 abuts against the contact portions 56 formed on the side and top surfaces of the sealing member 50, fixing the sealing member 50 together with the circulation component 40.

[0032] Therefore, neither the circulating component 40 nor the sealing member 50 will fall out of the through hole 32 of the nut 30. Furthermore, improper installation of the circulating component 40 and the sealing member 50 can be easily prevented. In addition, it is desirable from an aesthetic standpoint that the shape of the recess 57 does not protrude from the outer shape of the cap member 60 when viewed from above. The other configurations and operations are the same as those of the ball screw in the first embodiment.

[0033] In this embodiment, as shown in Figure 10, a sealing member 50A may be formed by integrally connecting a pair of sealing members 50 as a pair of sealing parts with a connecting part 59. The outer surface of the connecting part 59 is curved to be continuous with the contact part 56 formed on the upper surface of the pair of sealing parts 50, and the lower surface of the connecting part 59 abuts against the flat surface 33a of the nut 30.

[0034] In other words, in this modified example, when the sealing member 50A is fixed to the nut 30 with the cap member 60, the connecting portion 59 seals not only the pair of through holes 32 but also the space between the cap member 60 and the flat surface 33a of the nut 30. As a result, there are no metal-to-metal contact points on the outside of the nut 30, and all contact is between metal and resin or rubber with smaller gaps.

[0035] Therefore, not only is the assembly of the sealing member 50A made easier, but the leakage of grease that has leaked from the circulation part 40 into the cap member 60 to the outside can be effectively suppressed.

[0036] Furthermore, as shown in Figure 11, the shape shown in Figure 10 may be obtained by dividing the pair of connecting parts 59 and combining a pair of sealing members 50B of the same shape, each equipped with a connecting part 59.

[0037] Furthermore, as shown in Figures 12(a) and 12(b), the sealing member 50C has the end portion 71a of the upper edge portion 71 of the protrusion 55 extend outward from the opening edge of the through hole 32, so that the lower surface of the end portion 71a abuts against the outer circumferential surface 33 of the nut 30. This prevents wear of the sealing member 50C due to vibration caused by contact with the circulating component 40 due to the sealing member 50C penetrating too far into the nut 30, and prevents a decrease in grease leakage resistance.

[0038] Furthermore, the shape of the upper edge portion 71 of such a sealing member 50C may be such that the lower surface of the end portion 71a abuts against the surface of a notch formed around the opening edge of the through hole 32 of the nut 30 (for example, the surface of the notch 32c in Figure 5). Therefore, even in the sealing member 50 as in the first embodiment, the lower surface of the upper edge portion of the sealing member 50 abuts against the surface of the notch 32c, preventing it from penetrating too far into the nut 30.

[0039] Furthermore, as shown in Figure 13(a), the sealing member 50D may have a notch 62 formed on the peripheral edge between the outer surface 51 that contacts the inner surface of the through hole 32 of the nut 30 and the upper surface 53. As a result, as shown in Figure 13(b), when the sealing member 50D is inserted into the through hole 32 of the nut 30, a groove is formed by the inner surface of the through hole 32 and the notch 62 of the sealing member 50D. Then, by applying or pouring a sealant (not shown) such as clay, silicone, or caulking material into this groove, the adhesion between the sealing member 50D and the through hole 32 can be further improved, and grease leakage can be further reduced.

[0040] Furthermore, as shown in Figures 14(a) and 14(b), a notch 32a is formed along the opening edge of the through hole 32 of the nut 30, and a groove is formed between the notch 32a and the outer surface 51 of the sealing member 50C. In this case as well, by pouring sealing material into this groove, sealing can be achieved, making it more difficult for grease to leak.

[0041] Furthermore, the contact portion 56a of the sealing member 50C with the cap member 60 may be a combination of a curved surface 56a1 that matches the curved chamfered shape of the inner surface of the cap member 60, as shown in Figure 15(b), and a flat upper surface 56a2, thereby increasing the contact area with the inner surface of the cap member 60 and making it less likely for grease to leak.

[0042] On the other hand, as shown in Figure 15(a), the sealing member 50C1 may have a flat upper surface 56a3 for the contact portion 56a to partially contact the bottom surface of the cap member 60. Alternatively, depending on the shape of the inner surface of the cap member 60, the sealing member 50C2 shown in Figure 15(c) may have a combination of a stepped surface 56a4 and a flat upper surface 56a5 for the contact portion 56a to increase the contact area with the inner surface of the cap member 60.

[0043] Furthermore, the present invention is not limited to the embodiments and examples described above, and can be modified, improved, etc., as appropriate.

[0044] For example, as shown in Figure 16, the sealing member 50 has a substantially U-shaped outer surface 51, with the upper part being larger than the lower part. In other words, the side surface 51a of the substantially U-shaped outer surface 51 is formed in a tapered shape, gradually increasing in diameter from the bottom to the top.

[0045] Therefore, when the sealing member 50 is attached to the through hole 32 of the nut 30, the further the sealing member 50 is inserted into the through hole 32, the smaller the gap between the through hole 32 and the sealing member 50 becomes, and grease leakage can be further suppressed. In addition, displacement of the sealing member 50 can be prevented.

[0046] Furthermore, as shown in Figure 17, even if the scooping portion of the circulating component or load track is not oriented tangentially to the load track, grease leakage can be prevented by inserting the sealing member 50 into the gap between the through hole 32 of the nut 30 and the circulating component 40 to seal it.

[0047] Furthermore, since the tangential scooping type circulation component 40 is inserted diagonally into the through hole 32 of the nut 30, a gap is created to fill the sealing member 50. However, in the case of the tube-type circulation component shown in Figure 17, the shape of the through hole 32 of the corresponding nut 30 may not provide sufficient space for installing the sealing member. For this reason, such a through hole 32 may be provided with a space S into which the sealing member 50 fits, as shown in Figure 18. This makes it possible to reduce grease leakage even when the gap between the metal circulation component 40 and the through hole 32 of the nut 30 is large and grease is prone to leaking, by providing a space S into which the sealing member 50 fits and blocking the leaking grease with the sealing member 50.

[0048] Furthermore, the through-hole 32 is formed in a stepped shape with the bottom surface of the space S constituting the abutment surface 32b of the sealing member 50. This prevents the sealing member 50 from going in too far, and the contact between the abutment surface 32b and the sealing member 50 reduces grease leakage.

[0049] Furthermore, although the circulating component is made of metal in the above embodiment, it is not limited to this and may be made of resin.

[0050] As described above, the following matters are disclosed in this specification: (1) A screw shaft having a helical screw shaft side raceway groove formed on its outer surface, A nut having a nut-side raceway groove formed on its inner circumferential surface opposite to the screw shaft-side raceway groove, and a through hole provided that connects the outer circumferential surface and the nut-side raceway groove, Multiple balls that roll along a load track formed by the screw shaft side track groove and the nut side track groove, A circulating component attached to the through hole forms a ball return passage for circulating the balls that roll along the load track, A ball screw equipped with, A ball screw comprising a resin or rubber sealing member that seals at least a portion of the gap between the inner circumferential surface of the through hole of the nut and the outer circumferential surface of the circulating component. This configuration prevents grease from leaking through the gap between the circulating component and the through hole formed in the nut, and also prevents foreign matter from entering through the gap.

[0051] (2) The sealing member has a contact portion that contacts a cap member for fixing the circulating component to the nut so as to cover the circulating component, (1) The ball screw described above. With this configuration, the cap member can secure the sealing member to the nut together with the circulating component, preventing the sealing member from falling out of the through-hole.

[0052] (3) The sealing member comprises a main body portion that fits into the through hole of the nut, and a protrusion that protrudes outward from the main body portion and has the contact portion, (2) The ball screw described above. With this configuration, the cap member can secure the sealing member to the nut together with the circulating component, preventing the sealing member from falling out of the through-hole.

[0053] (4) The protrusion of the sealing member has an upper edge portion whose lower surface abuts against the outer surface of the nut, (3) The ball screw described above. This configuration prevents the sealing member from penetrating too far into the nut.

[0054] (5) The sealing member has an upper edge portion whose lower surface abuts against the surface of a notch formed at the opening edge of the through hole of the nut, (1) The ball screw described above.

[0055] (6) The sealing member has a notch formed at the edge between the outer surface that fits into the through hole of the nut and the upper surface, The notch forms a groove with the inner surface of the through hole. A ball screw as described in any of (1) to (5). With this configuration, by pouring sealant into the groove, it can be sealed and made less likely for grease to leak.

[0056] (7) A notch is formed on the outer surface of the nut along the opening edge of the through hole, The notched portion forms a groove with the outer surface of the sealing member. A ball screw as described in any of (1) to (5). With this configuration, by pouring sealant into the groove, it can be sealed and made less likely for grease to leak.

[0057] (8) The through hole of the nut is formed in a stepped shape with a stop surface that the lower surface of the sealing member abuts against. A ball screw as described in any of (1) to (7). This configuration prevents the sealing member from penetrating too far into the nut.

[0058] (9) When the sealing member is attached to the nut, the side surface of the sealing member is formed in a tapered shape that gradually widens from the bottom to the top. A ball screw as described in any of (1) to (8). With this configuration, the more the sealing member is pushed into the through hole, the smaller the gap between the through hole and the sealing member becomes, thus further suppressing grease leakage.

[0059] (10) The circulating component is provided with scooping portions at both ends for scooping up the ball from the load track, and each of the scooping portions is formed to be aligned with the tangential direction of the load track. A ball screw as described in any of (1) to (9). This configuration allows the balls rolling along the load track to be scooped up more smoothly by the scooping section, enabling high-speed operation.

[0060] This application is based on a Japanese patent application (Patent Application No. 2022-162549) filed on October 7, 2022, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0061] 10 Ball screws 20 Screw shaft 21 Screw shaft side raceway groove 25 Load track 26 balls 30 nuts 31 Nut-side raceway groove 32 Through holes 33 Outer surface 40 Circulation Parts 47 Scooping section 48 Ball return passage 50,50A Sealing member 51a Side view (side view of the sealing member) 56 Contact part 60 Cap component

Claims

1. A screw shaft having a helical screw shaft side raceway groove formed on its outer surface, A nut having a nut-side raceway groove formed on its inner circumferential surface opposite to the screw shaft-side raceway groove, and a through hole provided that connects the outer circumferential surface and the nut-side raceway groove, Multiple balls that roll along a load track formed by the screw shaft side track groove and the nut side track groove, A metal circulation component is attached to the through hole and forms a ball return passage for circulating the balls that roll along the load track, A ball screw equipped with, The nut is provided with a resin or rubber sealing member that seals at least a portion of the gap between the inner circumferential surface of the through hole and the outer circumferential surface of the circulating component, The circulating component is provided with scooping portions at both ends for scooping up the balls from the load track, and each of the scooping portions is formed to be aligned with the tangential direction of the load track. The sealing member has a substantially C-shaped inner surface that conforms to the shape of the outer surface of the circulating component. The sealing member is a ball screw in which the entire lower surface is positioned away from the ball return passage in the scooping portion and is installed in the gap between the through hole of the nut and the circulation component.

2. The sealing member has a contact portion that contacts a cap member for fixing the circulating component to the nut, so as to cover the circulating component. The ball screw according to claim 1.

3. The sealing member comprises a main body portion that fits into the through hole of the nut, and a protrusion that protrudes outward from the main body portion and has the contact portion. The ball screw according to claim 2.

4. The protrusion of the sealing member has an upper edge whose lower surface abuts against the outer circumferential surface of the nut or the surface of a notch formed at the opening edge of the through hole of the nut. The ball screw according to claim 3.

5. The sealing member has an upper edge portion whose lower surface abuts against the surface of a notch formed at the opening edge of the through hole of the nut. The ball screw according to claim 1.

6. The sealing member has a notch formed at the edge between the outer surface that fits into the through hole of the nut and the upper surface. The notch forms a groove with the inner surface of the through hole. The ball screw according to claim 1.

7. A notch is formed on the outer surface of the nut, along the opening edge of the through hole. The notched portion forms a groove with the outer surface of the sealing member. The ball screw according to claim 1.

8. The through hole of the nut is formed in a stepped shape and has a stopper surface that the lower surface of the sealing member abuts against. The ball screw according to claim 1.

9. When the sealing member is attached to the nut, the side surface of the sealing member is formed in a tapered shape that gradually widens from the bottom to the top. The ball screw according to claim 1 or 2.

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