Ball screw

Abstract

To provide an end cap type ball screw which enables balls to circulate smoothly while achieving reduction of costs of an end cap.SOLUTION: In a ball screw 1, a nut 3 has: a nut body 4 in which a female screw groove 12 is formed on an inner peripheral surface; and end caps 5 respectively assembled to one end and the other end of the nut body 4. The end cap 5 forms a connection passage 15 (16) which connects a spiral moving passage 13, formed by the female screw groove 12 and a male screw groove 11 of a screw shaft 2, with a return passage 14 which penetrates through the nut body in an axial direction at the radial outer side of the moving passage 13. The end cap 5 is a metallic component which is formed by a metal plate and assembled to the nut body 4, elastically compressed in the axial direction by the nut body 4.SELECTED DRAWING: Figure 5

Description

【Technical Field】 【0001】 The present invention relates to ball screws. 【Background Art】 【0002】 Patent Document 1 below describes a ball screw including a screw shaft and a nut that rotate relative to each other via a plurality of balls. The nut includes a nut body having a female screw groove formed in its inner peripheral surface, and end caps (referred to as "end deflectors" in the same document) as circulation members respectively assembled to one end and the other end of the nut body. In this ball screw, a spiral rolling path defined between a male screw groove formed in the outer peripheral surface of the screw shaft and the female screw groove facing the male screw groove, a return path penetrating the nut body in the axial direction outside the radial direction of the rolling path, and a set of connection paths formed by ball guide grooves provided in each end cap and connecting the rolling path and the return path form a series of ball circulation paths. As the screw shaft and the nut rotate relative to each other, a plurality of balls arranged in the ball passage circulate through the ball circulation paths. 【0003】 In the above ball screw, the end cap is made of resin, and the end cap is assembled to the nut body by a so-called snap fit in which locking claws provided on the end cap are engaged with the female screw groove of the nut body. With such a fixing method, the assembly of the end cap to the nut body can be easily carried out. When assembling the end cap to the nut body, the recess provided in the end cap may be fitted (engaged) with the protrusion provided in the nut body. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent No. 5411313 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 As with the ball screw described above, when a resin end cap is attached to the nut body using a snap-fit ​​mechanism, it is common practice to leave a gap between the locking claws of the end cap and the nut body to allow for some play in the end cap after it has been attached to the nut body. This is because if the resin end cap were attached to the nut body without any play using a snap-fit ​​mechanism, a load would continuously act on a part of the end cap (especially the locking claws), increasing the likelihood of creep and damage to the end cap. 【0006】 However, if play in the end cap is allowed, the relative positional relationship between the nut body and the end cap may be misaligned during the operation of the ball screw (when the screw shaft and nut rotate relative to each other), which may prevent the balls from moving smoothly through the ball circulation path. If the balls cannot move smoothly through the circulation path, problems such as an increase in the operating torque of the ball screw and the generation of abnormal noises and vibrations associated with the movement of the balls are more likely to occur. 【0007】 Furthermore, separate from the issues of operability and other related problems, when injection molding the end cap of Patent Document 1, which has a complex uneven shape, with resin, there are concerns about increased parts costs due to the complexity of the molding die and its drive mechanism. 【0008】 In view of the above concerns, the main objective of the present invention is to enable the smooth circulating movement of the balls in a so-called end cap type ball screw, while reducing the cost of the end cap, thereby stably achieving the desired operability. [Means for solving the problem] 【0009】 The present invention, devised to achieve the above objective, is a ball screw comprising a screw shaft and a nut that rotate relative to each other via a plurality of balls, wherein the nut has a nut body with an internal screw groove formed on its inner circumference and end caps assembled to one end and the other end of the nut body, and each end cap forms a connecting passage that connects a spiral turning path formed by an external screw groove formed on the outer circumference of the screw shaft and the internal screw groove, and a return passage that penetrates the nut body axially on the radially outer side of this turning path, and in a ball screw in which a plurality of balls circulate through a series of ball circulation paths having a turning path, a return passage and a set of connecting passages as the screw shaft and nut rotate relative to each other, the end cap is a metal part made of a metal plate and is assembled to the nut body in a state in which it is elastically compressed in the axial direction by the nut body. 【0010】 In the ball screw according to the present invention, the end cap is a metal part made from a metal plate. That is, the end cap can be, for example, a press-formed product formed into a predetermined shape by press-working a metal plate, or a metal part finished into a predetermined shape through laser processing (laser cutting) or press-working. In this way, in addition to being able to mass-produce end caps of a predetermined shape at low cost, it is possible to prevent creep from occurring in the end cap even when stress is continuously applied to the end cap as it is assembled to the nut body. Therefore, it is possible to prevent as much as possible the change in the assembly state of the end cap to the nut body (decreased assembly accuracy) over time. 【0011】 Furthermore, the end cap is assembled to the nut body in a state where it is elastically compressed in the axial direction by the nut body, that is, in a state where it is pressed axially against the nut body by its own axial elastic restoring force (a state where play is prevented). Therefore, even when multiple balls circulate through the ball circulation path as the screw shaft and nut rotate relative to each other, the relative positional relationship between the nut body and the end cap is less likely to be misaligned. These effects combined make it possible to realize a ball screw with excellent operational accuracy, where multiple balls can circulate smoothly through the ball circulation path, at a low cost. 【0012】 By the way, when balls circulate through the ball circulation path described above, "ball jams" are likely to occur where balls accumulate at the connection points between the ball circulation path and the connecting path, and at the connection points between the return path and the connecting path, where the direction of ball movement changes significantly. Therefore, it is preferable to assemble each end cap to the nut body in a state that allows for further elastic deformation in the axial direction. In this case, for example, by applying an outward axial pressure to the end cap, the end cap can be further compressed and deformed in the axial direction, which temporarily relieves the tight seal between the nut body and the end cap, making it easier to relieve ball jams at the aforementioned connection points. 【0013】 To reduce the cost of ball screws, it is preferable to use press-formed metal plates for the end caps. 【0014】 The end caps that form the connecting passages among the ball passages can be provided with ball guide grooves that form the connecting passages. These ball guide grooves can be formed by drawing or bending a metal plate. 【0015】 As in the ball screw described in Patent Document 1, if the end cap that forms part of the ball circulation path is made of resin, when grease is used as a lubricant for internal lubrication, swelling may occur depending on the type of resin material used to mold the end cap, thus limiting the types of grease that can be used. On the other hand, in the ball screw according to the present invention, since the end cap is a metal part, if the screw shaft, nut body and multiple balls are also made of metal (metal parts), the degree of freedom in selecting the grease to fill at least the running path of the ball circulation path can be increased. This makes it possible to easily realize a long-life ball screw in which internal lubrication is performed by grease. [Effects of the Invention] 【0016】 From the above, according to the present invention, in a so-called end-cap type ball screw, while reducing the cost of the end cap, it is possible to smoothly circulate and move the balls and stably exhibit desired operability. Therefore, the ball screw according to the present invention is characterized by being low-cost and having excellent operability with smooth circulation and movement of the balls. 【Brief Description of the Drawings】 【0017】 [Figure 1] Figure (a) is a front view of a ball screw according to an embodiment of the present invention, and figure (b) is a cross-sectional view taken along the arrow A-A in figure (a). [Figure 2] It is an exploded perspective view of the ball screw. [Figure 3] It is a partially enlarged view of FIG. 2. [Figure 4] Figure (a) is a perspective view of the end cap, and figure (b) is a perspective view of the same end cap when viewed from the side opposite to figure (a). [Figure 5] It is a cross-sectional view taken along the arrow B-B in FIG. 1(a). [Figure 6] It is a partially enlarged cross-sectional view of the part where the end cap is being assembled to the nut body. [Figure 7] It is a partially enlarged cross-sectional view showing the state where the end cap assembled to the nut body is elastically deformed. [Figure 8] Figure (a) is a perspective view of an end cap according to a modified example, and figure (b) is a perspective view of the same end cap when viewed from the side opposite to figure (a). 【Embodiments for Carrying Out the Invention】 【0018】 Hereinafter, embodiments of the present invention will be described based on the drawings. In the following description, the "axial direction" refers to the direction along the central axis of the screw shaft 2 constituting the ball screw 1, and the "circumferential direction" refers to the circumferential direction of a circle centered on the above central axis. 【0019】 Fig. 1(a) is a front view of the ball screw 1 according to an embodiment of the present invention, Fig. 1(b) is a cross-sectional view taken along the line A-A of Fig. 1(a), and Fig. 2 is an exploded perspective view of the ball screw 1. Based on these Figs. 1(a)(b) and Fig. 2, the overall structure of the ball screw 1 will be described. However, for the convenience of explaining the internal structure of the nut 3, the illustration of the screw shaft 2 is omitted in Figs. 1(a)(b). 【0020】 As shown in Figs. 1(a)(b) and Fig. 2, the ball screw 1 includes a screw shaft 2 having a helical male screw groove 11 formed on its outer peripheral surface, a nut 3 having a helical female screw groove 12 facing the male screw groove 11, and a plurality of balls 6 interposed in a rolling path 13 defined between the mutually facing male screw groove 11 and female screw groove 12. The screw shaft 2, the nut 3 (the nut body 4 and the end caps 5 which are components of the nut 3), and the balls 6 are all metal parts formed of a metal material. This ball screw 1 is used as a screw shaft rotation type in which the nut 3 moves forward and backward (linear motion) in the axial direction as the screw shaft 2 rotates around its axis, and a nut rotation type in which the screw shaft 2 moves forward and backward in the axial direction as the nut 3 rotates around its axis. In the ball screw 1 of the screw shaft rotation type, the rotation of the nut 3 is restricted by a rotation restricting means, and in the ball screw 1 of the nut rotation type, the rotation of the screw shaft 2 is restricted by a rotation restricting means. 【0021】 The nut 3 has a nut body 4 formed in a cylindrical shape and arc-shaped end caps 5, 5 respectively assembled to the ends (one end and the other end) on one side and the other side in the axial direction of the nut body 4. On one end face 4a and the other end face 4b of the nut body 4, arc-shaped recesses 7 recessed toward the central side in the axial direction of the nut body 4 are respectively formed, and the end caps 5 are assembled to these recesses 7. In the present embodiment, the end caps 5 respectively assembled to one end and the other end of the nut body 4 are the same parts. Therefore, the recesses 7 respectively formed on one end face 4a and the other end face 4b of the nut body 4 have the same shape and structure. 【0022】 The inner circumferential surface of the nut body 4 has the female screw groove 12 formed thereon. This female screw groove 12 defines a spiral track 13 on which the ball 6 rolls, opposite to the male screw groove 11 formed on the outer circumferential surface of the screw shaft 2. The nut body 4 also has a return passage 14 formed thereon, which is a through hole that penetrates the nut body 4 axially, radially outside the female screw groove 12. The through hole that serves as the return passage 14 is formed such that one end and the other end open to the inner bottom surface 7a of recesses 7 formed on one end face 4a and the other end face 4b, respectively. 【0023】 The end cap 5, assembled into the recess 7 on one end of the nut body 4, has a ball guide groove 5b provided therein that forms a connecting passage 15 connecting one end of the traffic path 13 and the return passage 14. Similarly, the end cap 5, assembled into the recess 7 on the other end of the nut body 4, has a ball guide groove 5b provided therein that forms a connecting passage 16 connecting the other ends of the traffic path 13 and the return passage 14. In this way, the nut 3 is provided with a series of ball passages 17 consisting of the traffic path 13, the return passage 14, and a pair of connecting passages 15 and 16. 【0024】 The balls 6 are continuously arranged within the ball passage 17 and circulate within the ball passage 17 as the screw shaft 2 and nut 3 rotate relative to each other. For example, in the case of a ball screw 1 of the screw shaft rotation type, when the screw shaft 2, which is the rotating side member, rotates forward around its axis, the balls 6 rolling within the running path 13 are introduced to one end of the return passage 14 via the connecting passage 15, and then introduced (reintroduced) into the running path 13 via the return passage 14 and the connecting passage 16. Also, when the screw shaft 2 rotates backward around its axis, the balls 6 rolling within the running path 13 are introduced to the other end of the return passage 14 via the connecting passage 16, and then introduced into the running path 13 via the return passage 14 and the connecting passage 15. In this manner, the circulating movement of the balls 6 within the ball passage 17 allows the nut 3, which is the linear side member, to move smoothly forward and backward. 【0025】 The ball screw 1 of this embodiment is primarily characterized by the assembly structure of the end cap 5 to the nut body 4, and therefore, this assembly structure will be described in detail below. As mentioned above, in this embodiment, the end caps 5 assembled to one end and the other end of the nut body 4 are the same part, and the recesses 7 into which these end caps 5 are actually assembled also have the same shape and structure. Therefore, the assembly structure of the end cap 5 on one end will be described as a representative example. 【0026】 First, as shown in an enlarged view in Figure 3, a fitting groove 8 is formed on the inner wall surface (inner surface) of the recess 7 into which the end cap 5 (the tips of the claw portions 5c and 5d provided on it) that is assembled into the recess 7 is fitted. The fitting groove 8 is defined between the first wall surface 8a and the second wall surface 8b (the inner bottom surface 7a of the recess 7), which are spaced apart in the axial direction, as shown in Figure 5, a cross-sectional view taken along the line BB in Figure 1(a). 【0027】 As shown in Figure 1(b), the end cap 5, which is assembled into the recess 7 at one end of the nut body 4, is assembled to the nut body 4 with its entire body housed in the recess 7, that is, with its axially outer end positioned on the same plane as the end face 4a of the nut body 4, or axially inward from the end face 4a (towards the axial center of the nut 3). 【0028】 The end cap 5 is a metal part made from a metal plate, in this case a press-formed product formed into a predetermined shape by press-working a metal plate. As shown in enlarged view in Figures 4(a) and 4(b), the end cap 5 has a base portion 5a formed in a substantially arc shape corresponding to the front view shape of the recess 7, a ball guide groove 5b formed by bulging a part of the base portion 5a outward in the axial direction, and claw portions 5c and 5d formed at the ends of the base portion 5a on one and the other sides in the circumferential direction, respectively. As also shown in Figure 5, a spring portion 5e formed in a substantially V-shape in cross-section is provided at the tip of the claw portion 5c, and this spring portion 5e is fitted into a fitting groove 8 formed on the inner surface of the recess 7 of the nut body 4 when the end cap 5 is assembled to the nut body 4. The axial dimension of the spring portion 5e (more specifically, the axial dimension of the spring portion 5e in a free state when the end cap 5 is not assembled to the nut body 4) is larger than the groove width d of the fitting groove 8 (see Figures 5 and 6). Although detailed illustrations are omitted, a spring portion 5e similar to the one described above is also provided at the tip of the claw portion 5d. 【0029】 In this embodiment, the end cap 5 is a press-formed metal plate product. A base portion 5a and claw portions 5c and 5d are obtained by punching out the metal plate. A ball guide groove 5b is obtained by drawing the base portion 5a (the part of the metal plate that becomes the base portion 5a), and a spring portion 5e is obtained by bending the tips of the claw portions 5c and 5d (the parts of the metal plate that become the claw portions 5c and 5d, which are punched out into a predetermined shape). 【0030】 The end cap 5 is assembled to the nut body 4 by moving the end cap 5 and the nut body 4 relatively closer together with the inner end face (axially inward end face) 5f of the end cap 5 facing the inner bottom surface 7a of the recess 7 of the nut body 4, as shown in Figure 6, and then fitting the end cap 5 into the inside of the recess 7. As described above, when the end cap 5 is assembled to the recess 4, the spring portion 5e provided at the tips of the claw portions 5c and 5d fits into the fitting groove 8 formed on the inner surface of the recess 4. Therefore, the fitting of the end cap 5 into the recess 7 proceeds with the tip side of the claw portions 5c and 5d elastically bending towards the base side of the claw portions 5c and 5d (see the white arrow in Figure 6). 【0031】 Then, when the inner end face 5f of the end cap 5 comes into contact with the inner bottom surface 7a of the recess 7, the bending stress acting on the tips of the claws 5c and 5d is released, and the claws 5c and 5d return to their natural state by elastic restoring force, and the spring portion 5e is fitted into the fitting groove 8. As mentioned above, since the groove width d of the fitting groove 8 is smaller than the axial dimension of the spring portion 5e in its free state, the spring portion 5e is fitted into the fitting groove 10 while being elastically compressed in the axial direction by the nut body 4. For this reason, the end cap 5 is assembled into the recess 7 of the nut body 4 with the elastic restoring force of the spring portion 5e pressing a part of the spring portion 5e against the axially outer edge (first wall surface 8a) of the fitting groove 8, and pressing its inner end face 5f against the inner bottom surface 7a (second wall surface 8b) of the recess 7. 【0032】 Furthermore, when the end cap 5 is assembled into the recess 7 of the nut body 4, the spring portion 5e of the end cap 5 is allowed to undergo further axial elastic deformation (elastic compressive deformation). Therefore, the end cap 5 is assembled into the recess 7 of the nut body 4 in a state that allows for further axial elastic deformation (elastic compressive deformation). 【0033】 When the end cap 5 is assembled to the recess 7 on one end of the nut body 4 as described above, the female screw groove 12 (and the resulting track 13) formed on the inner circumferential surface of the nut body 4 and one end of the return passage 14, which penetrates the nut body 4 axially on the radially outer side of the female screw groove 12, are connected via the ball guide groove 5b (and the resulting connecting passage 15) provided in the end cap 5. Similarly, when the end cap 5 is assembled to the recess 7 on the other end of the nut body 4, the other ends of the track 13 and the return passage 14 are connected via the ball guide groove 5b (and the resulting connecting passage 16) provided in the end cap 5. 【0034】 In the ball screw (end cap type ball screw) 1 of this embodiment described above, the end caps 5, which are press-formed metal plates attached to one end and the other end of the nut body 4, are assembled into the recesses 7 of the nut body 4 while being elastically compressed in the axial direction by the nut body 4 (more specifically, the spring portions 5e provided at the tips of the claw portions 5c and 5d of the end cap 5 are fitted into the fitting grooves 8 formed in the recesses 7 while being elastically compressed in the axial direction). 【0035】 Thus, by making the end cap 5 a press-formed metal plate, it is possible to mass-produce end caps 5 of a predetermined shape at low cost. In addition, it is possible to prevent creep from occurring in the end cap 5 even when stress is continuously applied to the end cap 5 during assembly to the nut body 4. Therefore, it is possible to prevent changes in the assembly state of the end cap 5 to the nut body 4 (decreased assembly accuracy) over time. 【0036】 Furthermore, the end cap 5 is assembled into the recess 7 of the nut body 4 in a state in which the spring portion 5e, integrally provided at the tips of its claw portions 5c and 5d, is elastically compressed in the axial direction by the two wall surfaces 8a and 8b that define the fitting groove 8 provided on the nut body 4. In other words, it is assembled into a state in which it is pressed axially against the nut body 4 by the axial elastic restoring force of the spring portion 5e, thus preventing rattle. For this reason, even if multiple balls 6 circulate through the ball circulation path 17 as the screw shaft 2 and the nut 3 rotate relative to each other, it is possible to prevent misalignment of the relative positional relationship between the nut body 4 and the end caps 5, 5. 【0037】 The combined effects of the above-mentioned features make it possible to realize a ball screw 1 at low cost that allows multiple balls 6 to smoothly circulate and move through the ball circulation path 17, resulting in excellent operational accuracy and the ability to maintain that state stably over a long period of time. 【0038】 Furthermore, in this embodiment, as described above, the end cap 5 is assembled into the recess 7 of the nut body 4 in a state that allows for further axial elastic deformation. In this way, for example, as shown in Figure 7, by applying an axially outward (away from the nut body 4) pressing force to the end cap 5 assembled to the nut body 4, the spring portion 5e fitted into the fitting groove 8 is further compressed and deformed in the axial direction, temporarily releasing the tight seal between the nut body 4 and the end cap 5, and creating a gap δ between the opposing inner end faces 5f of the end cap 5 and the inner bottom surface 4a of the recess 4. Therefore, even if a so-called "ball jam" occurs, where the direction of movement of the balls 6 circulating in the ball circulation path 17 changes significantly, and the balls 6 accumulate in the connecting portions of the turnout path 13 and connecting paths 15, 16, and the connecting portions of the return path 14 and connecting paths 15, 16, this can be easily and quickly resolved. 【0039】 Furthermore, if we consider the load (axial load) that presses the end cap 5 against the nut body 4 when the end cap 5 is assembled to the nut body 4 as Fz [unit: N], then designing the end cap 5 so that Fz satisfies the following relation (1) will enable the rapid resolution of the aforementioned "ball jamming". Fmin <Fz<Fmax ···(1) In the above relation (1), "Fmin" is the inertial force [unit: N] generated by axial vibration or shock acting on the ball screw 1, and is calculated by the following relation (2). In addition, "Fmax" in the above relation (1) is the force [unit: N] that propels the balls 6, which are continuously arranged outside the running path 13 of the ball circulation path 17 (i.e., within the return path 14 and a pair of connecting paths 15, 16), and is calculated by the following calculation formula (3). Fmin = [M + (m + C)] × B ... (2) Fmax = (Fa × sinθ) / A ... (3) Note that M: mass of end cap 5 [kg], m: mass of ball 6 [kg], C: number of balls 6 arranged outside the running path 13 in the ball circulation path 17, B: axial acceleration of ball 6 when vibration or shock acts on ball screw 1 [m / s²] 2 ], Fa: the maximum axial load acting on the ball screw 1 [N], θ: the lead angle of the ball center diameter (BCD) of the ball screw 1 [°], and A: the number of balls 6 arranged in the transfer path 13. 【0040】 Although a ball screw 1 according to one embodiment of the present invention has been described above, the ball screw 1 can be modified as appropriate without departing from the spirit of the present invention. 【0041】 For example, in the ball screw 1 described above, a nut 3 is used in which an end cap 5 having a ball guide groove 5b formed by drawing is assembled to a nut body 4. However, a nut 3 can also be used in which an end cap 5 having a ball guide groove 5b formed by bending is assembled to a nut body 4. Figure 8(a) is a perspective view of an example of an end cap 5 having a ball guide groove 5b formed by bending is viewed from the axial outside, and Figure 8(b) is a perspective view of the same end cap 5 viewed from the axial inside. In the illustrated example of the end cap 5, the ball guide groove 5b is defined by a pair of planes 5b1, 5b1 that are spaced apart and facing each other, and a curved surface 5b2 provided between the two planes 5b1, 5b1. 【0042】 Furthermore, the end cap 5 can be any metal part made from a metal sheet, and does not necessarily have to be a press-formed metal part. In other words, the end cap 5 may be a metal part formed into a predetermined shape by combining press working with other processing methods (for example, laser processing). 【0043】 Furthermore, in the ball screw 1 described above, the end cap 5 (and the recess 7 provided in the nut body 4 to accommodate it) is formed in an arc shape extending in the circumferential direction of the nut 3. However, the end cap 5 (and the recess 7) may be formed in other shapes such as circular or polygonal, as long as they can form predetermined connection paths 15 and 16. 【0044】 The present invention is not limited in any way to the embodiments described above, and can be implemented in various other forms without departing from the spirit of the invention. The scope of the present invention is indicated by the claims, and further includes all modifications within the meaning and scope of equivalents set forth in the claims. [Explanation of symbols] 【0045】 1 Ball screw 2 Screw shaft 3 nuts 4. Nut body 5 End caps 5b Ball guide groove 5c,5d Claw part 5e Spring section 6 balls 7 recesses 7a Inner bottom surface 8. Fitting groove 11 Male thread groove 12 Female thread grooves 13 Turning track 14 Return passage 15 connecting routes 16 connecting routes 17 Ball Circulation Route d Groove width

Claims

[Claim 1] It comprises a screw shaft and nut that rotate relative to each other via multiple balls, The nut comprises a nut body having an internal thread groove formed on its inner circumference, and end caps attached to one end and the other end of the nut body, respectively. Each end cap forms a connecting passage that connects a spiral path defined by a male thread groove and a female thread groove formed on the outer circumferential surface of the screw shaft, and a return passage that penetrates the nut body axially on the radially outer side of the path. In a ball screw in which a plurality of balls circulate through a series of ball circulation paths having a turnaway path, a return path, and a set of connecting paths, as the screw shaft and the nut rotate relative to each other, The ball screw is characterized in that the end cap is a metal part made of a metal plate and is assembled to the nut body in a state in which it is elastically compressed in the axial direction by the nut body. [Claim 2] The ball screw according to claim 1, wherein the end cap is assembled to the nut body in such a way that further axial elastic deformation is permitted. [Claim 3] The ball screw according to claim 1 or 2, wherein the end cap is a press-formed product of a metal plate. [Claim 4] The ball screw according to claim 1 or 2, wherein the end cap has a ball guide groove that forms the connection path, and the ball guide groove is formed by drawing. [Claim 5] The ball screw according to claim 1 or 2, wherein the end cap has a ball guide groove that forms the connection path, and the ball guide groove is bent. [Claim 6] The ball screw according to claim 1 or 2, wherein the screw shaft, the nut body, and the plurality of balls are made of metal, and at least the ball circulation path is filled with grease.