Ball screw

Abstract

The ball screw includes a threaded shaft having a first helical thread groove on its outer circumferential surface, a nut attached to the outer circumferential side of the threaded shaft, having a second helical thread groove on its inner circumferential surface, being movable in the longitudinal direction of the threaded shaft and having an elongated hole penetrating in the radial direction, a plurality of balls that roll in a rolling path formed between the first thread groove and the second thread groove, and a top member attached to the nut so as to cover the elongated hole and provided with a circulation path for guiding the balls so that they climb over the threads of the first threaded shaft and enter the adjacent rolling path. The top member includes a first member provided with a first groove constituting a part of the circulation path, a second member provided with a second groove constituting a part of the circulation path and combined with the first member to form the circulation path, a greasing member having a contact portion exposed to the circulation path side and contacting the balls, and a third member that holds the greasing member so as to cover the outer diameter side of the greasing member.

Description

[Technical field]

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

[0002] 2. Description of the Related Art A ball screw including a screw shaft, a nut, a plurality of balls, and a top member for circulating the balls is known (see, for example, Patent Documents 1, 2, 3, and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-54710 A [Patent Document 2] JP 2015-232346 A [Patent Document 3] JP 2018-40455 A [Patent Document 4] JP 2010-71411 A Summary of the Invention [Problem to be solved by the invention]

[0004] Ball screws are required to ensure smooth ball rolling and circulation over a long period of time, and they also need to be easy to use during maintenance and assembly.

[0005] Therefore, one of the objects is to provide a ball screw that can improve workability while ensuring smooth rolling and circulation of the balls over a long period of time. [Means for solving the problem]

[0006] A ball screw according to the present disclosure includes a threaded shaft having a first helical thread groove on its outer circumferential surface, a nut attached to the outer circumferential side of the threaded shaft, having a second helical thread groove on its inner circumferential surface, movable in the longitudinal direction of the threaded shaft, and having an elongated hole penetrating in the radial direction, a plurality of balls rolling in a rolling path formed between the first thread groove and the second thread groove, and a top member attached to the nut so as to cover the elongated hole and provided with a circulation path for guiding the balls so that the balls pass over the threads of the first threaded shaft and enter the adjacent rolling path. The top member includes a first member provided with a first groove constituting a part of the circulation path, a second member provided with a second groove constituting a part of the circulation path and combined with the first member to form the circulation path, a greasing member having a contact portion exposed to the circulation path side and contacting the balls, and a third member that holds the greasing member so as to cover the outer diameter side of the greasing member. Effect of the Invention

[0007] According to the above-described ball screw, smooth rolling and circulation of the balls can be ensured for a long period of time, while improving workability. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view of a ball screw according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic side view of the ball screw shown in FIG. [Diagram 3] FIG. 3 is a schematic cross-sectional view of a portion taken along the cross section indicated by III-III in FIG. [Figure 4] FIG. 4 is a schematic perspective view showing a nut included in the ball screw. [Diagram 5] FIG. 5 is a schematic perspective view showing the appearance of the piece member. [Figure 6] FIG. 6 is an exploded perspective view of the link member. [Figure 7] FIG. 7 is a schematic cross-sectional view of a part of the piece member. [Figure 8] FIG. 8 is a schematic perspective view of the link member as viewed from the inner diameter side of the nut. [Figure 9] FIG. 9 is a schematic perspective view showing a state in which the first member and the second member are combined. [Figure 10] FIG. 10 is a schematic perspective view showing a state in which the first member and the second member are combined. [Figure 11] FIG. 11 is a schematic perspective view showing the first member. [Figure 12] FIG. 12 is a schematic perspective view showing the second member. [Figure 13] FIG. 13 is a schematic perspective view showing the third member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Outline of the embodiment] The ball screw of the present disclosure includes a threaded shaft having a first helical thread groove on its outer circumferential surface, a nut attached to the outer circumferential side of the threaded shaft, having a second helical thread groove on its inner circumferential surface, movable in the longitudinal direction of the threaded shaft, and having an elongated hole penetrating in the radial direction, a plurality of balls that roll in a rolling path formed between the first thread groove and the second thread groove, and a top member attached to the nut so as to cover the elongated hole and provided with a circulation path for guiding the balls so that they climb over the threads of the first threaded shaft and enter the adjacent rolling path. The top member includes a first member provided with a first groove constituting a part of the circulation path, a second member provided with a second groove constituting a part of the circulation path and combined with the first member to form the circulation path, a greasing member having a contact portion exposed to the circulation path side and contacting the balls, and a third member that holds the greasing member so as to cover the outer diameter side of the greasing member.

[0010] According to the ball screw of the present disclosure, the top member is not composed of one part, but is composed of a combination of a first member, a second member, a third member, and a greasing member. The circulation path is formed by combining the first groove and the second groove. In this way, for the members other than the greasing member, it is possible to select and combine members of appropriate materials and shapes according to the function required for the circulation path and ease of installation. Since the greasing member has a contact portion exposed to the circulation path and in contact with the balls, the contact portion can graze the balls passing through the circulation path. In this way, it is possible to ensure smooth rolling and circulation of the balls for a long period of time. In addition, since the third member is arranged to cover the outer diameter side of the greasing member, the greasing member is not exposed to the outer diameter side, and as a result, it is possible to prevent the greasing member from drying out. Since the greasing member is held by the third member, when replacing the greasing member, the third member can be removed from the nut. In this way, the lubrication member can be replaced without removing the first member and the second member from the nut, which reduces the risk of an increase in assembly man-hours and improves workability. As described above, with the above ball screw, it is possible to improve workability while ensuring smooth rolling and circulation of the balls over a long period of time.

[0011] In the ball screw, the greasing member may be plate-shaped. In this way, the thickness direction of the greasing member is arranged in the radial direction of the ball screw, and a relatively large amount of lubricating oil can be impregnated into the greasing member while suppressing an increase in volume, particularly in the radial direction. In addition, the handleability of the greasing member can be improved.

[0012] In the above ball screw, the greasing member may be held so as to be sandwiched between the third member and the second member. In this way, the position of the greasing member can be stably maintained within the top member. Therefore, the balls can be greased more stably for a long period of time.

[0013] In the above ball screw, the contact portion may have a protruding region that protrudes toward the circulation path. The second member may be provided with a housing groove that houses the protruding region. In this manner, the lubricating oil can be gradually exuded from the protruding region to grease the balls. In this case, since the protruding region is housed in the housing groove, it is possible to stably hold the protruding region and suppress deviation of the grease supply position. Therefore, it is possible to more reliably grease the balls for a long period of time.

[0014] In the above ball screw, the protruding length of the protruding region may be 30% or more and 70% or less of the diameter of the ball. This allows the ball and the protruding region to be in contact with each other reliably. Therefore, the ball can be more reliably greased. More preferably, the protruding length of the protruding region is selected to be 40% or more and 60% or less of the diameter of the ball.

[0015] In the above ball screw, the third member may be provided with an accommodating recess for accommodating the greasing member. In this way, the greasing member can be fitted and accommodated in the accommodating recess provided in the third member, and the greasing member can be held more stably. In addition, the third member can be attached by fitting the greasing member into the accommodating recess, improving workability.

[0016] In the above ball screw, the first member and the third member may each be attached to the nut by a screw. The second member may be sandwiched between the first member and the third member. In this way, the first member and the third member can be reliably fixed to the nut by the screw, and the first member and the third member can be removed by turning the screw. In addition, since the second member is sandwiched between the first member and the third member, it can be more reliably fixed to the nut side. In other words, by adopting such a configuration, it is possible to easily attach and detach the top member. This makes it easy to replace the grease supply member. Therefore, it is possible to further improve the workability.

[0017] In the above-mentioned ball screw, a plurality of the bearing members may be provided at intervals in the circumferential direction. In this way, the plurality of balls can be smoothly circulated by the plurality of bearing members. Therefore, the balls can be circulated more smoothly.

[0018] [Specific Example of the Embodiment] Next, an example of a specific embodiment of the ball screw of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals and the description thereof will not be repeated.

[0019] (Embodiment 1) First, a first embodiment of the present disclosure will be described. FIG. 1 is a schematic perspective view of a ball screw in the first embodiment of the present disclosure. FIG. 2 is a schematic side view of the ball screw shown in FIG. 1. FIG. 2 is a view seen in the opposite direction to the direction of the arrow Y shown in FIG. 1. FIG. 3 is a schematic cross-sectional view of a part cut at the cross section shown by III-III in FIG. 1. In the figures shown in FIG. 1 and subsequent figures, the direction shown by the arrow Z is the longitudinal direction of a screw shaft described later, and the directions shown by the arrows X and Y are radial directions. The direction shown by the arrows X and Y are perpendicular to each other.

[0020] 1, 2, and 3, a ball screw 10a in the first embodiment includes a screw shaft 11a, a nut 12a, balls 13a as rolling elements, and a plurality of, in the present embodiment, three, piece members 14a. For example, steel balls are used as the balls 13a. The screw shaft 11a has a shape extending in the longitudinal direction (Z direction). A first screw groove 16a having a helical shape is provided on the outer circumferential surface of the screw shaft 11a over the entire longitudinal area. When the ball screw 10a is viewed from the side, a first screw thread 17a is arranged between adjacent first screw grooves 16a.

[0021] FIG. 4 is a schematic perspective view showing a nut 12a included in the ball screw 10a. Referring also to FIG. 4, the nut 12a is attached to the outer periphery of the screw shaft 11a. The nut 12a includes a hollow cylindrical tubular portion 21a and a flange portion 22a arranged on one side in the longitudinal direction of the tubular portion 21a. The flange portion 22a is rectangular when viewed from the thickness direction, which is the longitudinal direction of the screw shaft 11a, specifically, a quadrangle with four chamfered corners. The nut 12a has a shape in which the tubular portion 21a and the flange portion 22a are connected in the longitudinal direction.

[0022] The nut 12a, specifically, the cylindrical portion 21a included in the nut 12a, is provided with a plurality of elongated holes 23a, 23b, and 23c penetrating in the radial direction, in this embodiment, three. The cylindrical portion 21a is provided with three recesses 24a whose outer circumferential surface is recessed toward the inner diameter side, specifically at intervals of 120 degrees in the circumferential direction. The elongated holes 23a, 23b, and 23c are provided in the regions where the three recesses 24a are located. The elongated holes 23a are provided at intervals in the circumferential direction. In this embodiment, the elongated holes 23a, 23b, and 23c are provided at intervals in the circumferential direction. The elongated holes 23a, 23b, and 23c are also provided at intervals in the axial direction (longitudinal direction (Z direction)). The elongated holes 23a, 23b, and 23c are provided at an inclination in the axial direction. Each of the long holes 23a, 23b, and 23c opens so as to straddle two adjacent first screw grooves 16a when viewed from the outer diameter side when the nut 12a is attached to the outer periphery of the screw shaft 11a. The two first screw grooves 16a straddled by the long holes 23a, 23b, and 23c are offset from each other by one. A top member 14a for circulating the ball 13a is attached to each of the long holes 23a, 23b, and 23c. This will be described in detail later. A plurality of screw holes for attaching the top member 14a are provided around the long holes 23a, 23b, and 23c. Four through holes for attaching other members to the nut 12a are provided near the four corners of the flange portion 22a.

[0023] A second helical screw groove 18a is provided on the inner peripheral surface of the nut 12a. A plurality of balls 13a are arranged in a rolling path 19a formed between the first screw groove 16a and the second screw groove 18a. The balls 13a roll in the rolling path 19a. The nut 12a can move in the longitudinal direction of the screw shaft 11a as the balls 13a circulate while rolling. The nut 12a can perform linear reciprocating motion with respect to the screw shaft 11a.

[0024] The nut 12a includes a first annular seal ring 25a attached to one side in the longitudinal direction where the cylindrical portion 21a is disposed, and a second annular seal ring 26a attached to the other side in the longitudinal direction where the flange portion 22a is disposed. The first seal ring 25a is fitted into a first fitting recess 27a provided on the inner circumferential side of the cylindrical portion 21a, and the second seal ring 26a is fitted into a second fitting recess 28a provided on the inner circumferential side of the flange portion 22a. The first seal ring 25a and the second seal ring 26a each have a thread groove formed on their inner circumferential surfaces that mesh with the first thread groove 16a of the screw shaft 11a.

[0025] Next, the configuration of the piece member 14a will be described. The piece member 14a is attached to the nut 12a so as to cover each of the three long holes 23a, 23b, and 23c provided in the nut 12a as described above. The piece member 14a is provided with a circulation path 29a that guides the balls 13a in a given first screw groove 16a so that the balls 13a in the given first screw groove 16a can climb over the threads of the screw shaft 11a and enter the adjacent first screw groove 16a. The ball screw 10a is provided with a scoop 15a that sequentially supplies the balls 13a from the rolling path 19a to the circulation path 29a.

[0026] The piece member 14a includes a first member 31a, a second member 32a, a third member 33a, and a greasing member 34a. The first member 31a, the second member 32a, and the third member 33a are made of rigid members, for example, metal. Specifically, the first member 31a, the second member 32a, and the third member 33a are made of at least one of a resin such as polyacetal, carbon steel, and stainless steel.

[0027] FIG. 5 is a schematic perspective view showing the appearance of the piece member 14a. FIG. 6 is an exploded perspective view of the piece member 14a. FIG. 7 is a schematic cross-sectional view of the piece member 14a when a part of the piece member 14a is cut. FIG. 8 is a schematic perspective view of the piece member 14a seen from the inner diameter side of the nut 12a. FIGS. 9 and 10 are schematic perspective views showing a state in which the first member 31a and the second member 32a are combined. FIGS. 9 and 10 are views seen from different angles. FIG. 11 is a schematic perspective view showing the first member 31a. FIG. 12 is a schematic perspective view showing the second member 32a. FIG. 13 is a schematic perspective view showing the third member 33a. In order to facilitate understanding, a plurality of rolling balls 13a are also shown in FIGS. 5, 7, and 8, and the first screw 42a is also shown in FIG. 9.

[0028] 5 to 13, the first member 31a is provided with a first groove 36a that constitutes a part of the circulation path 29a. The first member 31a has a first contact surface 37a that contacts the second member 32a when combined with the second member 32a. The second member 32a is provided with a second groove 38a that constitutes a part of the circulation path 29a. The second member 32a has a second contact surface 39a that contacts the first member 31a when combined with the first member 31a. The shape of the second contact surface 39a corresponds to the shape of the first contact surface 37a. The first member 31a and the second member 32a are combined so that the first contact surface 37a and the second contact surface 39a are in contact with each other, thereby forming the circulation path 29a that is composed of the first groove 36a and the second groove 38a.

[0029] The first member 31a is provided with a first mounting hole 41a for mounting the first member 31a to the nut 12a. The first mounting hole 41a is a round hole. The first mounting hole 41a has a shape with a portion of different diameters so that the body of the first mounting screw 42a passes through and the head of the screw 42a is hooked. For example, a flat head screw is used as the first screw 42a and a second screw 47a described later. When the first screw 42a is inserted into the first mounting hole 41a and tightened, the head of the first screw 42a fits within the first mounting hole 41a. The second member 32a is provided with an accommodation groove 43a for accommodating a protruding region 53a of a contact portion 52a of a grease supply member 34a described later.

[0030] The grease supply member 34a is plate-shaped. More specifically, the grease supply member 34a is flat. The grease supply member 34a is also called an oil-containing member. The grease supply member 34a is made of a member impregnated with lubricating oil, for example. Specifically, the grease supply member 34a is made of a porous sintered resin member that is heated and molded and impregnated with a lubricant. Alternatively, a solid lubricant may be used that is obtained by mixing a powder of a sintered resin member and a lubricant and then heating and molding the mixture.

[0031] The grease supply member 34a includes a flat plate portion 51a and a contact portion 52a exposed on the circulation path 29a side and in contact with the ball 13a. The flat plate portion 51a is polygonal when viewed in the thickness direction. The contact portion 52a has a protruding region 53a protruding from the flat plate portion 51a to the circulation path 29a side. The ball 13a is greased, that is, lubricating oil is supplied to the ball 13a by seeping out from the protruding region 53a. The lubricating oil impregnated in the flat plate portion 51a region is gradually supplied to the protruding region 53a side. In this embodiment, the protruding length L of the protruding region 53a is 30% or more and 70% or less of the diameter D of the ball 13a. In this embodiment, the protruding length L of the protruding region 53a is 40% or more and 60% or less of the diameter D of the ball 13a. (See especially FIG. 5 and FIG. 6). In this embodiment, the length of protrusion of protruding region 53a toward circulation path 29a indicated by arrow P in FIG. 7 is, for example, 40% to 60% of protruding length L of protruding region 53a in FIG.

[0032] The third member 33a holds the grease supply member 34a so as to cover the outer diameter side of the grease supply member 34a. The third member 33a is provided with a storage recess 45a for storing the grease supply member 34a. The storage recess 45a is shaped to be recessed along the outer shape of the plate-shaped grease supply member 34a, mainly along the outer shape of the flat plate portion 51a. The third member 33a is provided with a second mounting hole 46a for mounting the third member 33a to the nut 12a side. The second mounting hole 46a is a round hole. The second mounting hole 46a, like the first mounting hole 41a, has a shape having a portion with a different diameter so that the body of the second mounting screw 47a passes through and the head is hooked. The third member 33a is provided with a third contact surface 48a that contacts the first contact surface 37a of the first member 31a during mounting.

[0033] The first member 31a is attached to the nut 12a by a first screw 42a. The third member 33a is attached to the nut 12a by a second screw 47a. The second member 32a is sandwiched between the first member 31a and the third member 33a. The greasing member 34a is sandwiched between the second member 32a and the third member 33a.

[0034] The attachment of the piece member 14a is briefly described as follows. The first member 31a and the second member 32a are assembled so that the first contact surface 37a and the second contact surface 39a are in contact with each other, and the first member 31a is fixed to the nut 12a using the first screw 42a. In this case, the body of the first screw 42a is passed through the first mounting hole 41a, and the first screw 42a is attached using a screw hole provided in the nut 12a to fix the first member 31a. Next, the grease supply member 34a is accommodated in the accommodation recess 45a, and the third member 33a is applied from the outer diameter side so that the protruding region 53a of the contact portion 52a is accommodated in the accommodation groove 43a of the second member 32a. Alternatively, the grease supply member 34a is placed from the outer diameter side so that the protruding region 53a of the contact portion 52a is accommodated in the accommodation groove 43a of the second member 32a, and the third member 33a is attached from the outer diameter side so that the grease supply member 34a is accommodated in the accommodation recess 45a. In these cases, the grease supply member 34a is sandwiched between the second member 32a and the third member 33a in the radial direction. After that, the third member 33a is fixed to the nut 12a using the second screw 47a so that the first contact surface 37a and the third contact surface 48a are in contact with each other. In this case, the body of the second screw 47a is passed through the second mounting hole 46a, and the second screw 47a is attached using a screw hole provided in the nut 12a to fix the third member 33a.

[0035] According to the ball screw 10a having the above-mentioned configuration, the top member 14a is not composed of one part, but is composed of a combination of the first member 31a, the second member 32a, the third member 33a, and the greasing member 34a. The circulation path 29a is formed by combining the first groove 36a and the second groove 38a. In this way, for the members other than the greasing member 34a, it is possible to select and combine members of appropriate materials and shapes according to the function required for the circulation path 29a and ease of installation. The greasing member 34a has a contact portion 52a that is exposed to the circulation path 29a and contacts the ball 13a, so that the contact portion 52a can graze the ball 13a passing through the circulation path 29a. This ensures smooth rolling and circulation of the ball 13a for a long period of time. In addition, since the third member 33a is arranged to cover the outer diameter side of the greasing member 34a, the greasing member 34a is not exposed to the outer diameter side, and as a result, it is possible to prevent the greasing member 34a from drying out. Since the greasing member 34a is held by the third member 33a, when replacing the greasing member 34a, the third member 33a can be removed from the nut 12a. This allows the greasing member 34a to be replaced without removing the first member 31a and the second member 32a from the nut 12a, reducing the risk of an increase in assembly man-hours and improving workability. As described above, the ball screw 10a can improve workability while ensuring smooth rolling and circulation of the balls 13a for a long period of time.

[0036] In this embodiment, the grease supply member 34a is plate-shaped. Therefore, the thickness direction of the grease supply member 34a is arranged in the radial direction of the ball screw 10a, and the grease supply member 34a can be impregnated with a relatively large amount of lubricating oil while suppressing an increase in volume, particularly in the radial direction. In addition, the grease supply member 34a can be easily handled.

[0037] In this embodiment, the grease supply member 34a is held in a sandwiched manner between the third member 33a and the second member 32a. Therefore, the position of the grease supply member 34a can be stably maintained within the piece member 14a. Therefore, the ball 13a can be greased more stably for a long period of time.

[0038] In this embodiment, the contact portion 52a has a protruding region 53a that protrudes toward the circulation path 29a. The second member 32a is provided with a housing groove 43a that houses the protruding region 53a. Thus, the lubricant gradually seeps out from the protruding region 53a to grease the ball 13a. In this case, since the protruding region 53a is housed in the housing groove 43a, the protruding region 53a can be stably held and the displacement of the grease supply position can be suppressed. Therefore, the ball 13a can be greased more reliably for a long period of time.

[0039] In this embodiment, the protruding length L of the protruding region 53a is 30% to 70% of the diameter D of the ball 13a. This allows the ball 13a to come into contact with the protruding region 53a more reliably. This allows the ball 13a to be greased more reliably.

[0040] In this embodiment, the third member 33a is provided with a storage recess 45a for storing the grease supply member 34a. Therefore, the grease supply member 34a can be fitted and stored in the storage recess 45a provided in the third member 33a, and the grease supply member 34a can be held more stably. In addition, the grease supply member 34a can be fitted into the storage recess 45a to attach the third member 33a, improving workability.

[0041] In this embodiment, the first member 31a and the third member 33a are attached to the nut 12a by the screws 42a and 47a, respectively. The second member 32a is sandwiched between the first member 31a and the third member 33a. Therefore, the first member 31a and the third member 33a can be reliably fixed to the nut 12a by the screws 42a and 47a, and the first member 31a and the third member 33a can be removed by turning the screws 42a and 47a. In addition, since the second member 32a is sandwiched between the first member 31a and the third member 33a, it can be more reliably fixed to the nut 12a side. That is, by adopting such a configuration, it is possible to easily attach and detach the top member 14a. Then, it is possible to easily replace the grease supply member 34a. Therefore, it is possible to further improve the workability.

[0042] In this embodiment, a plurality of the piece members 14a are provided at intervals in the circumferential direction. Therefore, the plurality of the balls 13a can be smoothly circulated by the plurality of the piece members 14a. Therefore, the balls 13a can be circulated more smoothly.

[0043] (Other embodiments) In the above embodiment, three oblong holes and three top members are provided, but this is not limited thereto, and the ball screw may have two oblong holes and two top members, or four or more.

[0044] In addition, in the above embodiment, the contact portion and the rolling surface of the ball are in contact with each other on the outer diameter side of the ball, but this is not limited to the above, and the contact portion and the rolling surface of the ball may be in contact with each other on one side in the axial direction of the ball.

[0045] In the above embodiment, the grease supply member is plate-shaped, but the grease supply member is not limited to this, and may be, for example, block-shaped or spherical.

[0046] In addition, in the above embodiment, the first member and the third member are attached to the nut side by screws, but this is not limited thereto, and the first member and the third member may be attached to the nut side by, for example, a snap fit.

[0047] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not restrictive in any respect. The scope of the present invention is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. [Explanation of symbols]

[0048] 10a ball screw, 11a screw shaft, 12a nut, 13a ball, 14a piece member, 15a scoop, 16a first screw groove, 17a first screw thread, 18a second screw groove, 19a rolling path, 21a cylindrical portion, 22a flange portion, 23a, 23b, 23c long hole, 24a recess, 25a first seal ring, 26a second seal ring, 27a first fitting recess, 28a second fitting recess, 29a circulation path, 31a first member, 32a second member, 33a third member, 34a greasing member, 36a first groove, 37a first contact surface, 38a second groove, 39a second contact surface, 41a first mounting hole, 42a screw (first screw), 43a accommodation groove, 45a Accommodating recess, 46a second mounting hole, 47a screw (second screw), 48a third contact surface, 51a contact portion, 52a protruding region.

Claims

1. a screw shaft having a first spiral thread groove provided on an outer peripheral surface thereof; A nut attached to the outer circumferential side of the screw shaft, having a spiral second screw groove on its inner circumferential surface, being movable in the longitudinal direction of the screw shaft, and having a long hole penetrating in the radial direction; a plurality of balls that roll in a rolling path formed between the first screw groove and the second screw groove; a ball member attached to the nut so as to cover the elongated hole, the ball being provided with a circulation path that guides the ball so that the ball in a predetermined first screw groove passes over the thread of the screw shaft and enters the adjacent first screw groove; The piece member is a first member provided with a first groove that forms part of the circulation path; a second member having a second groove that forms a part of the circulation path and that is combined with the first member to form the circulation path; a grease supply member having a contact portion exposed to the circulation path side and contacting the ball; a third member that holds the grease supply member so as to cover an outer diameter side of the grease supply member.

2. The ball screw according to claim 1 , wherein the greasing member is plate-shaped.

3. 3. The ball screw according to claim 1, wherein the greasing member is held by being sandwiched between the third member and the second member.

4. the contact portion has a protruding region that protrudes toward the circulation path, 3. The ball screw according to claim 1, wherein the second member is provided with an accommodation groove that accommodates the protruding region.

5. 5. The ball screw according to claim 4, wherein a protruding length of the protruding region is equal to or greater than 30% and equal to or less than 70% of a diameter of the ball.

6. 3. The ball screw according to claim 1, wherein the third member is provided with an accommodating recess for accommodating the grease supply member.

7. the first member and the third member are each attached to the nut by a screw; 3. The ball screw according to claim 1, wherein the second member is sandwiched between the first member and the third member.

8. 3. The ball screw according to claim 1, wherein a plurality of the bearing members are provided at intervals in the circumferential direction.

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