Ball screw

Abstract

To provide a ball screw capable of effectively circulating and supplying lubricant to a ball rolling path and a ball returning passage without increasing the size of a nut.SOLUTION: The ball screw includes a screw shaft 20 formed with a screw shaft side track groove 21, a nut 30 formed with a nut side track groove 31 and provided with a through-hole 32 for communicating an outer peripheral face 33 and the nut side track groove 31 with each other, a plurality of balls 26, a circulation component 40 having a ball returning passage 48 for scooping and circulating the balls 26 rolling on the ball rolling path 25, and a sealing member 50 for sealing a gap between the inner peripheral face of the through-hole 32 and the outer peripheral face of the circulation component 40, the circulation component 40 having a nut insertion part 46 to be inserted into the through-hole 32 when mounted to the nut 30, and a grease circulation hole 41 provided in the nut insertion part 46 for communicating the through-hole 32 and the ball returning passage 25 with each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a ball screw, and more particularly to a ball circulating type ball screw in which balls as rolling elements circulate outside a nut. [Background technology]

[0002] In ball-recirculating ball screws used in machine tools and the like, the balls arranged in a spiral ball rolling path (loaded track) consisting of the screw shaft side raceway groove of the screw shaft and the nut side raceway groove of the nut must be scooped up from the ball rolling path and returned from one end of the ball rolling path to the other end.

[0003] Known ball circulation methods include the tube type, the top type (also called the deflector type), the end cap type, and the end deflector type. Of these, a ball circulation type ball screw, which circulates balls outside the nut, is equipped with a circulation part having a ball return passage for picking up and circulating the balls rolling on the ball rolling path.

[0004] In such a ball screw, the ball rolling path and the ball return passage are lubricated to extend the rolling fatigue life of the ball screw. By lubricating the ball rolling path and the ball return passage with a lubricant, the frictional force acting on the surfaces of the screw shaft side raceway groove and the nut side raceway groove can be reduced and stress can be alleviated, thereby extending the rolling fatigue life of the ball screw.

[0005] Therefore, the inside of the nut of the ball screw is filled with a lubricant such as grease, and in order to retain the grease and prevent foreign matter from entering from the outside, a seal is provided in the gap between the screw shaft and the nut, and a sealing member is provided in the gap between the through hole of the nut and the circulation part.

[0006] In addition, for example, in a screw device with a lubricant application function described in Patent Document 1, an application part that contacts the rolling element rolling grooves (screw shaft side raceway grooves) of the screw shaft to apply lubricant is provided in a return member (circulation part). A lubricant storage chamber and a lubricant passage for supplying lubricant to the application part are separately provided in the nut. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3948973 Summary of the Invention [Problem to be solved by the invention]

[0008] However, grease accumulates near the sealing member that is attached to the open end on the outer peripheral side of the through hole and seals the gap between the inner peripheral surface of the through hole and the outer peripheral surface of the circulation part. The grease that accumulates near the sealing member for a long time may gradually leak out in small amounts from the small gap in the sealing member due to vibrations caused by the ball screw drive, or oil that has separated from the grease may gradually seep out, resulting in the grease being unable to contribute to lubrication. Furthermore, in a screw device with a lubricant application function as disclosed in Patent Document 1, a lubricant storage chamber is separately provided on the outer periphery or end face of the nut, which results in an increase in the size of the nut.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a ball screw that can effectively circulate and supply lubricant to the ball rolling path and the ball return passage without increasing the size of the nut. [Means for solving the problem]

[0010] 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; a nut having an inner peripheral surface formed with a spiral nut-side raceway groove facing the screw shaft-side raceway groove, and having a pair of through holes communicating an outer peripheral surface with the nut-side raceway groove; a plurality of balls rolling in a ball rolling path formed by the screw shaft side raceway groove and the nut side raceway groove; a circulation part attached to the through hole and having a ball return passage for scooping up and circulating the balls rolling along the ball rolling path; a sealing member attached to an open end of the through hole on the outer circumferential surface side thereof to seal a gap between an inner circumferential surface of the through hole and an outer circumferential surface of the circulation part; A ball screw comprising: The circulation component has a nut insertion portion that is inserted into the through hole when the circulation component is attached to the nut, and an opening portion for grease circulation that is provided in the nut insertion portion and communicates between the through hole and the ball return passage. A ball screw characterized by: Effect of the Invention

[0011] According to the ball screw of the present invention, the lubricant can be effectively circulated and supplied to the ball rolling path and the ball return passage without increasing the size of the nut. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view of a ball screw according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of the ball screw shown in FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a main portion for explaining the operation of the ball screw shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the circulatory device shown in FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of a main portion for explaining the operation of the ball screw according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of the circulatory device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a ball screw according to the present invention will be described in detail with reference to the drawings. (First embodiment) First, a ball screw 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. As shown in Figures 1 and 2, the ball screw 10 of the first embodiment comprises a screw shaft 20 having a spiral screw shaft side raceway groove 21 formed on its outer peripheral surface, a nut 30 having a spiral nut side raceway groove 31 (see Figure 3) formed on its inner peripheral surface facing the screw shaft side raceway groove 21 and having a pair of through holes 32 connecting the outer peripheral surface 33 and the nut side raceway groove 31, a plurality of balls 26 rollably interposed in a ball rolling path 25 formed by the screw shaft side raceway groove 21 and the nut side raceway groove 31, a circulation part 40 having a ball return passage 48 for scooping up and circulating the balls 26 rolling in the ball rolling path 25, and a sealing member 50 attached to the opening end of the through hole 32 on the outer peripheral surface 33 side and sealing the gap between the inner peripheral surface of the through hole 32 and the outer peripheral surface of the circulation part 40.

[0014] The ball screw 10 of the first embodiment is configured to include two circulation parts 40, but the number of circulation parts 40 can be set to any number depending on the number of ball return passages 48. 2 and 3, the circulation part 40 is formed by bending a metal pipe member, and has a straight part 45 that is 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 parts 46 in which both ends of the straight part 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. Furthermore, a scooping part 47 is provided at the tip of each of the nut insertion parts 46.

[0015] As shown in Figure 4, the ball return passage 48 of the circulation part 40 has a gothic arc shape, which is approximately a V-shape formed by combining two identical circular arcs with different centers of curvature, and has a pair of inner surface grooves 49 that extend opposite each other along the central axis C.

[0016] A hole 41 is drilled in the nut outer diameter side surface (upper side surface in FIG. 4) of the nut insertion portion 46 as an opening for grease circulation that communicates between the through hole 32 and the ball return passage 48. The circular hole 41 is drilled so as to be continuous with the inner surface groove 49 of the ball return passage 48, so that the opening edge of the hole 41 and the ball 26 do not come into contact with each other.

[0017] The sealing member 50 is a member that seals the gap between the through hole 32 of the nut 30 and the circulation part 40, and is made of an elastic material such as resin or rubber.

[0018] 3, when the circulation part 40 is attached to the nut 30, each scooping part 47 is disposed in a direction along the tangential direction of the ball rolling path 25. As a result, the circulation part 40 forms a ball return passage 48 that scoops up the balls 26 rolling in the ball rolling path 25 with the scooping parts 47 from the tangential direction of the central orbit circle D and returns the balls 26 to the other position of the ball rolling path 25.

[0019] Although the circulation part 40 is formed by bending a metal pipe member, the present invention is not limited to this, and the circulation part 40 may be formed into a pipe shape by combining two parts that are split along the central axis.

[0020] Furthermore, as shown in Figures 1 and 2, the ball screw 10 is provided with a cap member 60 as a circulatory component holding member that is fitted to cover the circulatory component 40 and fixed to the outer peripheral surface 33 of the nut 30 by a set screw 70 inserted into the fixing hole 63. The cap member 60 includes a holding groove (not shown) having a generally U-shaped cross section that covers the straight portion 45 of the circulation part 40 and holds it immovable, and a flange portion 61 in which two fixing holes 63 are formed.

[0021] Nut insertion portions 46 , which are both ends of the circulation component 40 , are inserted into a pair of through holes 32 formed by communicating the outer circumferential surface 33 of the nut 30 with the nut side raceway groove 31 . At this time, the nut insertion portion 46, which is disposed in a direction along the tangential direction of the ball rolling path 25, is disposed obliquely, not parallel, to the central axis of the through hole 32, as shown in Fig. 3. Therefore, a substantially wedge-shaped space is defined near the sealing member 50 of the through hole 32 by the nut outer diameter side surface of the nut insertion portion 46, the inner circumferential surface of the through hole 32, and the inner side surface of the sealing member 50.

[0022] Thereafter, a sealing member 50 is attached from above to the gap between the through hole 32 of the nut 30 and the circulation part 40. This seals the gap between the through hole 32 and the circulation part 40, preventing the grease G, which is a lubricant, from leaking from inside the nut 30 and preventing foreign matter from entering from the outside.

[0023] Next, the cap member 60 is placed over the circulation part 40 and the sealing member 50, and is fixed to the outer peripheral surface 33 of the nut 30 by screwing the set screw 70 inserted through the fixing hole 63 into the screw hole 35 formed in the flat surface 33a.

[0024] Next, the effects of the ball screw 10 of the first embodiment will be described. In order to extend the rolling fatigue life of the ball screw 10, lubrication is performed with grease G. The grease G is filled, for example, from a grease nipple (not shown) of the nut 30 or directly applied to the screw shaft side raceway groove 21 of the screw shaft 20, and then a break-in stroke of the ball screw 10 is performed to allow the grease G to permeate every corner of the nut 30.

[0025] When the ball screw 10 is in use, multiple balls 26 roll and circulate through the ball rolling path 25 and the ball return passage 48, causing grease G to accumulate in the approximately wedge-shaped space of the nut 30 defined near the sealing member 50 of the through hole 32, as shown in Figure 3.

[0026] And, a hole 41 communicating with a ball return passage 48 is drilled in the outer diameter side surface of the nut insertion portion 46 facing the approximately wedge-shaped space of the nut 30, so that the grease G accumulated in the approximately wedge-shaped space can be returned to the ball return passage 48 in accordance with the ball circulation. That is, the grease G accumulated in the approximately wedge-shaped space near the sealing member 50 of the through hole 32, or the separated oil, can be returned to the ball return passage 48 through the hole 41 provided in the circulation part 40, and the grease G can be effectively utilized.

[0027] Furthermore, when the circulation speed of balls 26 is high and grease G flows from the ball return passage 48 side of circulation part 40 to the side of through hole 32 near sealing member 50 through hole 41 provided in circulation part 40, grease G that has accumulated in the approximately wedge-shaped space near sealing member 50 can be pushed toward nut-side raceway groove 31 of nut 30. That is, grease G that leaks to the side of through hole 32 near sealing member 50 through hole 41 provided in circulation part 40 pushes grease G that has accumulated in the approximately wedge-shaped space toward nut-side raceway groove 31 of nut 30, and the grease G can be effectively utilized.

[0028] In addition, since the gap between the sealing member 50 and the circulation part 40 and the through hole 32 is smaller than the gap between the tip side of the nut insertion portion 46 and the through hole 32, there is almost no effect on the leakage of grease G to the outside of the nut.

[0029] As described above, in the ball screw 10 of the first embodiment, there is no need to provide a separate lubricant storage chamber on the outer periphery or end face of the nut 30, and by returning the grease G accumulated near the sealing member 50 of the through hole 32 to the ball return passage 48 of the circulation part 40, it is possible to effectively utilize the grease G and thereby reduce the amount of greasing, thereby contributing to reducing the environmental impact.

[0030] In the ball screw 10 according to the first embodiment, the hole 41 serving as an opening for grease circulation that connects the through hole 32 with the ball return passage 48 is drilled in the outer diameter side surface of the nut of the nut insertion portion 46. That is, the hole 41 can be easily formed by a boring process using a drill or the like.

[0031] Furthermore, in the ball screw 10 according to the first embodiment, the hole 41 that communicates between the through hole 32 and the ball return passage 48 is continuous with the inner surface groove 49 of the ball return passage 48, whose cross-sectional shape is a Gothic arc shape. Therefore, the opening edge of the hole 41 does not come into contact with the ball 26, and damage to the ball 26 can be prevented.

[0032] In the ball screw 10 of the first embodiment, the hole 41 is located on the nut outer diameter side surface of the nut insertion portion 46. In contrast, if the hole 41 is located on the nut inner diameter side surface (the lower surface in FIG. 4) of the nut insertion portion 46, the end of the hole 41 will be outside the ball rolling path 25 in which the balls 26 roll, and little effect of grease circulation can be expected, so this is not a suitable position for the hole 41.

[0033] Second embodiment Next, a ball screw 10A according to a second embodiment of the present invention will be described with reference to FIGS. A ball screw 10A of the second embodiment has a circulating part 40A that is different from the circulating part 40 of the first embodiment. In the following, the same parts as those of the first embodiment are denoted by the same or corresponding reference characters, and detailed description thereof will be omitted.

[0034] The ball screw 10A of the second embodiment includes a circulation component 40A having a ball return passage 48 for picking up the balls 26 rolling in the ball rolling paths 25 and circulating them. The circulation part 40A is formed in a pipe shape by integrally combining a first circulation part 42 and a second circulation part 43, each of which has a shape divided into two parts along the central axis.

[0035] The first circulatory part 42 and the second circulatory part 43 are produced by, for example, press molding of a metal plate, injection molding of a synthetic resin, metal powder injection molding, or the like. 5 and 6, a notched hole 41A is formed on the mating surface of the first circulation part 42 and the second circulation part 43 as an opening for grease circulation that communicates between the through hole 32 and the ball return passage 48. Note that the semicircular notched hole 41A is desirably formed on the mating surface of the first circulation part 42 that is disposed on the nut outer diameter side of the nut insertion part 46.

[0036] Therefore, according to the ball screw 10A of the second embodiment, as with the ball screw 10 of the first embodiment described above, there is no need to separately provide a lubricant storage chamber on the outer periphery or end face of the nut 30, and by returning the grease G accumulated near the sealing member 50 of the through hole 32 to the ball return passage 48 of the circulating part 40A, it is possible to effectively utilize the grease G and thereby reduce the amount of greasing, thereby contributing to reducing the environmental impact.

[0037] In the ball screw 10A according to the second embodiment, a notched hole 41A serving as an opening for grease circulation that connects the through hole 32 and the ball return passage 48 is formed in the mating surface of the first circulation part 42. Thus, the notched hole 41A can be formed simultaneously when the first circulation part 42 is molded, and the notched hole 41A can be formed without additional processing such as drilling.

[0038] Therefore, according to the ball screws 10, 10A according to the above embodiments, the lubricant can be effectively circulated and supplied to the ball rolling path 25 and the ball return passage 48 without increasing the size of the nut 30.

[0039] It goes without saying that the shapes of the hole 41 and the notched hole 41A in each of the above embodiments are not limited to those described above and may take various shapes. However, it is preferable that the maximum width of the hole 41 or the notched hole 41A is ¼ or less of the ball diameter of the ball 26. In other words, if the maximum width of the hole 41 or the notched hole 41A exceeds ¼ of the ball diameter, the ball 26 and the opening edge will come into contact in the ball return passage 48, which is likely to affect the service life.

[0040] In addition, the position at which the hole 41 or the notched hole 41A is provided is the part that goes inward from the outer diameter of the nut when the circulation parts 40, 40A are attached to the nut 30 (the nut insertion part 46 inserted into the through hole 32), and it is preferable that it does not interfere with the sealing member 50 and is as close to the sealing member 50 as possible.

[0041] 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.

[0042] 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].

[0043] [1] A screw shaft (20) having a spiral screw shaft side raceway groove (21) formed on an outer circumferential surface thereof; a nut (30) having a spiral nut-side raceway groove (31) formed on its inner peripheral surface in opposition to the screw shaft-side raceway groove (21) and having a pair of through holes (32) communicating between its outer peripheral surface (33) and the nut-side raceway groove (31); a plurality of balls (26) rolling in a ball rolling path (25) formed by the screw shaft side raceway groove (21) and the nut side raceway groove (31); a circulation component (40, 40A) attached to the through hole (32) and having a ball return passage (48) for scooping up and circulating the balls (26) rolling in the ball rolling path (25); a sealing member (50) attached to an open end of the through hole (32) on the outer circumferential surface side, and configured to seal a gap between an inner circumferential surface of the through hole (32) and an outer circumferential surface of the circulation part (40, 40A); A ball screw comprising: The circulation component (40, 40A) has a nut insertion portion (46) that is inserted into the through hole (32) when the circulation component (40, 40A) is attached to the nut (30), and an opening portion (hole 41, notched hole 41A) for grease circulation that is provided in the nut insertion portion (46) and communicates between the through hole (32) and the ball return passage (25). A ball screw (10, 10A) characterized in that

[0044] According to the ball screw (10, 10A) having the configuration [1] above, there is no need to provide a separate lubricant storage chamber on the outer periphery or end face of the nut (30). The grease (G) accumulated near the sealing member (50) of the through hole (32) is returned to the ball return passage (48) of the circulation part (40, 40A). This makes it possible to effectively utilize the grease (G) and reduce the amount of greasing required, thereby contributing to a reduction in the environmental load.

[0045] [2] The opening is a hole (41) drilled on the outer diameter side surface of the nut of the nut insertion portion (46). The ball screw (10) according to the above [1].

[0046] According to the ball screw (10) having the configuration [2] above, the hole (41) can be easily formed by boring using a drill or the like.

[0047] [3] The hole (41) is connected to an inner surface groove (49) of the ball return passage (48) having a Gothic arc cross-sectional shape. The ball screw (10) according to the above item [2].

[0048] According to the ball screw (10) having the configuration [3] above, the opening edge of the hole (41) does not come into contact with the ball (26), so that the ball (26) can be prevented from being damaged.

[0049] [4] The opening is a notched hole (41A) formed in a mating surface of the circulation part (40A) composed of multiple parts (first circulation part 42 and second circulation part 43). The ball screw (10A) according to the above [1].

[0050] According to the ball screw (10A) having the configuration [4] above, the cutout hole (41A) can be formed simultaneously when molding at least one part (first circulating part 42), and the cutout hole (41A) can be formed without additional processing such as drilling.

[0051] [5] The maximum width of the hole (41) or the notched hole (41A) is 1 / 4 or less of the ball diameter of the ball (26). The ball screw (10, 10A) according to any one of the above items [2] to [4].

[0052] According to the ball screw (10, 10A) having the configuration [5] above, it is possible to reduce the possibility that the balls (26) will come into contact with the opening edge in the ball return passage (48), which may adversely affect the service life. [Explanation of symbols]

[0053] 10. Ball screw 20 Screw shaft 21 Screw shaft side raceway groove 25 Ball Rolling Path 26 Ball 30 Nut 31 Nut side raceway groove 32 Through hole 33 Outer surface 40 Rotating Parts 41 Hole (Opening) 46 Nut insertion part 48 Ball return passage 50 Sealing member

Claims

1. a screw shaft having a helical screw shaft side raceway groove formed on an outer circumferential surface; a nut having an inner peripheral surface formed with a spiral nut-side raceway groove facing the screw shaft-side raceway groove, and having a pair of through holes communicating with an outer peripheral surface and the nut-side raceway groove; a plurality of balls rolling in a ball rolling path formed by the screw shaft side raceway groove and the nut side raceway groove; a circulation part attached to the through hole and having a ball return passage for scooping up and circulating the balls rolling along the ball rolling path; a sealing member attached to an open end of the through hole on the outer circumferential surface side thereof, the sealing member sealing a gap between an inner circumferential surface of the through hole and an outer circumferential surface of the circulation part; A ball screw comprising: The circulation component has a nut insertion portion that is inserted into the through hole when the circulation component is attached to the nut, and an opening portion for grease circulation that is provided in the nut insertion portion and communicates between the through hole and the ball return passage. A ball screw characterized by:

2. The opening is a hole drilled on the outer diameter side surface of the nut insertion portion.

2. The ball screw according to claim 1 .

3. The hole is continuous with an inner groove of the ball return passage having a gothic arc cross-sectional shape.

3. The ball screw according to claim 2.

4. The opening is a notch hole formed in a mating surface of the circulation component composed of a plurality of parts.

2. The ball screw according to claim 1 .

5. The maximum width of the hole or the notch hole is ¼ or less of the ball diameter of the ball.

5. The ball screw according to claim 2, wherein the ball screw is a ball bearing.

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