Nut and ball screw device

Abstract

A nut according to the present disclosure is provided with: a cylindrical nut body through which a screw shaft passes; a plurality of inner circumferential raceway surfaces and a plurality of S-shaped groove surfaces that are recessed radially outward from the inner circumferential surface of the nut body; and a flange that protrudes radially outward from the outer circumferential surface of the nut body. The flange is configured from at least one partial flange extending only in a part in the circumferential direction along the outer circumferential surface of the nut body. When the number of the partial flanges is one, the space between one end and the other end of the partial flange in the circumferential direction is a retreat space in which the wall portion of the nut body is retreated, and when the number of the partial flanges is two or more, the space between the partial flanges adjacent in the circumferential direction is a retreat space in which the wall portion of the nut body is retreated. One of the plurality of S-shaped groove surfaces is disposed on the radially inner side of the relief space.

Description

Technical Field

[0001] The present disclosure relates to a nut and a ball screw arrangement. Background Art

[0002] The ball screw device includes a screw shaft, a nut through which the screw shaft passes, and a plurality of balls arranged between the screw shaft and the nut. An outer peripheral track surface is provided on the outer peripheral surface of the screw shaft. An inner peripheral track surface opposite to the outer peripheral track surface is provided on the inner peripheral surface of the nut. A spiral track is formed between the outer peripheral track surface and the inner peripheral track surface. A plurality of balls are arranged on the track. In addition, the ball screw device includes a circulation portion for circulating the balls. As an example of the circulation portion, an S-shaped groove surface formed on the inner peripheral surface of the nut can be cited. According to the S-shaped groove surface, a ball that has moved one lead can be returned by one lead. In addition, as described in the following patent document, the nut sometimes has a flange protruding radially outward.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent document 1: European Patent Application Publication No. 003208164 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, when an S-shaped groove surface is formed on the inner circumferential surface of the nut by forging, if there is a flange on the radially outer side, it is difficult for the wall portion of the nut to retreat radially outward, and it is difficult to form the S-shaped groove surface. For this reason, the S-shaped groove surface is formed offset relative to the flange in the axial direction. On the other hand, since the S-shaped groove surface and the inner circumferential raceway surface are not provided on the radially inner side of the flange, there is a problem that the nut is enlarged in the axial direction.

[0008] The present disclosure has been made in view of the above-mentioned circumstances, and an object of the present disclosure is to provide a nut capable of avoiding enlargement in the axial direction and a ball screw device including the nut.

[0009] Solutions for solving problems

[0010] In order to achieve the above-mentioned purpose, a nut of a technical solution of the present disclosure comprises: a nut body, which is cylindrical and through which a screw shaft passes; a plurality of inner circumferential track surfaces and a plurality of S-shaped groove surfaces, which are recessed radially outward from the inner circumferential surface of the nut body; and a flange, which protrudes radially outward from the outer circumferential surface of the nut body. The flange is composed of at least one partial flange extending only in a part of the circumferential direction along the outer circumferential surface of the nut body. In the case where there is one partial flange, the space between one end and the other end of the partial flange in the circumferential direction is a retreat space for the wall portion of the nut body to retreat, and in the case where there are two or more partial flanges, the space between the adjacent partial flanges in the circumferential direction is a retreat space for the wall portion of the nut body to retreat. One of the plurality of S-shaped groove surfaces is arranged radially inward relative to the retreat space.

[0011] According to the present disclosure, the wall portion of the nut body can be retreated to the retreat space. That is, an S-shaped groove surface can be formed by forging in a portion of the nut body that is arranged radially inward relative to the retreat space. As a result, it is not necessary to form the S-shaped groove surface in an axially offset manner relative to the flange (partial flange), thereby avoiding the nut from being enlarged in the axial direction. In addition, according to the present disclosure, the nut is also lightweight compared to the case where the flange is annular.

[0012] As a preferred technical solution of the nut, the plurality of S-shaped groove surfaces are arranged at equal intervals in the circumferential direction.

[0013] The nut supports the screw shaft from the radial outside by means of balls. In addition, the inner circumferential raceway surface extends in the circumferential direction, and the range of support from the radial outside is in the entire circumferential direction. On the other hand, the portion in the circumferential direction where the S-shaped groove surface is provided cannot support the screw shaft from the radial outside. According to the structure, the range in which the screw shaft cannot be supported from the radial outside is dispersed in the circumferential direction. Therefore, the screw shaft can be supported from all directions in the circumferential direction.

[0014] In the nut, the flange may include two or more partial flanges arranged at equal intervals in the circumferential direction.

[0015] As a preferred technical solution of the nut, a shaft supported by a housing and extending axially parallel to the screw shaft is arranged radially outside the partial flange. A sliding groove surface recessed radially inward and accommodating the shaft is provided on the outer peripheral surface of the partial flange.

[0016] According to the above configuration, the nut is supported by the housing in a manner that is non-rotatable and axially movable.

[0017] As a preferred technical solution of the nut, the planetary gear of the planetary gear mechanism and the partial flange are opposite to each other in an axial direction parallel to the screw shaft. The partial flange is provided with a hole for inserting a transmission shaft supporting the planetary gear.

[0018] According to the above structure, the rotational motion of the planetary gears revolving around the sun gear is transmitted to the partial flange. Therefore, a planetary carrier supporting the planetary gears is not required, and the number of parts is reduced.

[0019] As a preferred technical solution of the nut, the nut body is arranged inside the driven pulley. The partial flange is inserted into a groove provided on the inner peripheral surface of the driven pulley.

[0020] According to the above configuration, the nut rotates integrally with the driven pulley.

[0021] As a preferred technical solution of the nut, a protrusion is provided on one end face of the nut body, which protrudes in the axial direction and contacts a stopper that does not rotate relative to the screw shaft. The S-shaped groove surface that is closest to the protrusion in the axial direction among the multiple S-shaped groove surfaces is arranged to be offset in the circumferential direction relative to the protrusion.

[0022] According to the above structure, the contact load generated by the stopper acts on the protrusion, which can avoid the S-shaped groove surface disposed close to the ground from being deformed. In addition, the protrusion can be prevented from being deformed by the load when forging the inner peripheral surface of the nut. In other words, the initial position deviation can also be avoided.

[0023] In order to achieve the above-mentioned object, a ball screw device of the present disclosure includes: a screw shaft; the nut; and a plurality of balls arranged between the screw shaft and the nut.

[0024] According to the present disclosure, it is possible to avoid the nut from being enlarged in the axial direction. In addition, the nut can be made lighter compared to the case where the flange is annular.

[0025] Effects of the Invention

[0026] According to the present disclosure, it is possible to avoid an increase in size of the nut in the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a cross-sectional view of the brake booster according to the first embodiment, cut along the axial direction in a state before being actuated.

[0028] Figure 2 It is magnified Figure 1 An enlarged view of a portion of the nut is shown.

[0029] Figure 3 This is a diagram when the nut according to the first embodiment is viewed from the second direction.

[0030] Figure 4 This is a perspective view when the nut of the first embodiment is viewed from an angle from the second direction.

[0031] Figure 5 yes Figure 1 Sectional view taken along line VV.

[0032] Figure 6 This is a diagram when the nut of Modification 1 is viewed from the second direction.

[0033] Figure 7 This is a view of the flange unconnected region of the nut of Modification 2 as viewed from the second direction.

[0034] Figure 8 This is a perspective view of the nut of Modification 3 viewed from the second direction.

[0035] Fig. 9 This is a diagram when the nut of Modification 3 is viewed from the second direction.

[0036] Fig.10 yes Fig. 9 Magnified image of .

[0037] Fig.11 This is a perspective view of the nut according to the second embodiment when viewed from the second direction.

[0038] Fig.12 This is a diagram when the nut of Modification 4 is viewed from the second direction.

[0039] Fig.13 This is a perspective view of the nut according to the third embodiment when viewed from the second direction.

[0040] Fig.14 This is a diagram when the nut according to the third embodiment is viewed from the second direction. DETAILED DESCRIPTION

[0041] The embodiments for implementing the present disclosure are described in detail with reference to the accompanying drawings. The present disclosure is not limited to the contents described in the following description. In addition, the structural elements described below include elements that can be easily thought of by those skilled in the art, and substantially the same elements. Moreover, the structural elements described below can be appropriately combined.

[0042] (Implementation Method 1)

[0043] Figure 1This is a cross-sectional view of the brake booster of Embodiment 1 cut along the axial direction in a state before operation. In Embodiment 1, an example of applying the electric actuator of the present disclosure to a brake booster of a brake system is given for illustration. In addition, the electric actuator of the present disclosure can also be applied to other devices such as brake calipers in addition to the brake booster shown in the embodiment.

[0044] like Figure 1 As shown, the electric actuator 100 of the first embodiment includes a housing 101, a motor (not shown), a planetary gear mechanism 110, a ball screw device 1, a piston 50, and a stopper 60. Hereinafter, the direction parallel to the central axis O of the screw shaft 2 of the ball screw device 1 is referred to as an axial direction. In addition, in the axial direction, the direction in which the piston 50 is arranged when viewed from the planetary gear mechanism 110 is referred to as a first direction X1, and the opposite direction to the first direction is referred to as a second direction X2.

[0045] A cylinder body 102 is provided at the end of the housing 101 in the first direction X1. The cylinder body 102 has a cylindrical portion 103 that is cylindrical with the central axis O as the center, and a closed wall 104 that closes the opening of the cylindrical portion 103 in the first direction X1. The piston 50 is inserted into the opening of the cylindrical portion 103 in the second direction X2. Therefore, the internal space of the cylinder body 102 is closed. A liquid not shown in the figure is sealed in the internal space of the cylinder body 102. A through hole 104a is provided in the closed wall 104. If the piston 50 moves in the first direction X1, the hydraulic pressure of the liquid rises. Then, the rising hydraulic pressure is transmitted to the brake system via the through hole 104a.

[0046] The planetary gear mechanism 110 includes an input shaft 111 , a sun gear 112 , a ring gear 113 , a plurality of planetary gears 114 , a plurality of transmission shafts 115 , and a carrier 116 .

[0047] The rotational motion of the motor is input to the input shaft 111. The input shaft 111 is arranged coaxially with the central axis O. The sun gear 112 penetrates the input shaft 111 and is fixed to the input shaft 111 in a non-rotatable manner. The ring gear 113 is an internal gear centered on the input shaft 111. The outer peripheral surface of the ring gear 113 is fitted with the housing 101.

[0048] The planetary gear 114 is disposed between the sun gear 112 and the ring gear 113. The planetary gear 114 meshes with the sun gear 112 and the ring gear 113. The transmission shaft 115 penetrates the planetary gear 114. The planetary gear 114 is supported so as to be rotatable about the transmission shaft 115.

[0049] The planetary carrier 116 is an annular member centered on the central axis O. The outer peripheral surface of the planetary carrier 116 is engaged with the inner ring of the bearing 117. Therefore, the planetary carrier 116 is supported by the housing 101 in a rotatable manner. The screw shaft 2 passes through the central part of the planetary carrier 116. The planetary carrier 116 and the screw shaft 2 are splined. Therefore, the planetary carrier 116 and the screw shaft 2 are connected in a manner that cannot rotate relative to each other. In addition, the transmission shaft 115 passes through a position eccentric to the radial outside from the central part of the planetary carrier 116.

[0050] As described above, according to the planetary gear mechanism 110, when the rotational motion is input to the input shaft 111, the sun gear 112 rotates around the central axis O. Then, the planetary gear 114 rotates (rotates) around the transmission shaft 115 while rotating (revolves) around the central axis O. As a result, the planetary carrier 116 and the screw shaft 2 rotate around the central axis O. In addition, the rotation speed of the screw shaft 2 is slower than the rotation speed of the input shaft 111.

[0051] The ball screw device 1 includes a screw shaft 2, a nut 10, and a plurality of balls 8. The screw shaft 2 includes a male spline portion 3 connected to a planetary carrier 116, and a screw shaft body 4 arranged in a first direction X1 relative to the male spline portion 3. An outer peripheral track surface 5 extending in a spiral direction is provided on the outer peripheral surface of the screw shaft body 4.

[0052] The diameter of the male spline portion 3 is smaller than the diameter of the screw shaft body 4. Therefore, a step surface 6 facing the second direction X2 is provided between the male spline portion 3 and the screw shaft body 4. The step surface 6 abuts against the side of the stopper 60. In addition, the stopper 60 abuts against the side of the planetary carrier 116. Therefore, the screw shaft 2 is fixed in a manner that cannot move in the second direction X2. In addition, the male spline portion 3 is pressed into the planetary carrier 116, and the screw shaft 2 is fixed in a manner that cannot move in the first direction X1. In addition, the present disclosure may also be that the male spline portion 3 is clearance-fitted with respect to the planetary carrier 116. In such a case, it is also possible that a retaining ring abutting against the planetary carrier 116 from the second direction X2 is provided on the male spline portion 3 to prevent the screw shaft 2 from falling off. In addition, in the present disclosure, a caulking portion that abuts against the planetary carrier 116 from the second direction X2 may be provided instead of a retaining ring, or the planetary carrier 116 and the male spline portion 3 may be welded instead of a retaining ring.

[0053] Figure 2 It is magnified Figure 1 An enlarged view of a portion of the nut is shown. Figure 2 As shown, the nut 10 includes a nut body 11 , a plurality of inner peripheral raceway surfaces 12 , a plurality of S-shaped groove surfaces 13 , a flange 20 , and a protrusion 30 .

[0054] The nut body 11 is cylindrical with the central axis O as the center. The nut body 11 has a first end face 10a facing the first direction X1 and a second end face 10b facing the second direction X2. The first end face 10a is a pressing piston 50 (see Figure 1 )’s pressing surface.

[0055] The inner peripheral raceway surface 12 and the plurality of S-shaped groove surfaces 13 are groove surfaces provided on the inner peripheral surface 11a of the nut body 11. The inner peripheral raceway surface 12 and the outer peripheral raceway surface 5 of the screw shaft 2 (see Figure 1 ) and extend in the spiral direction. The inner raceway surface 12 extends one turn (one lead) in the spiral direction. A track 7 is formed between each inner raceway surface 12 and the outer raceway surface 5 (refer to Figure 1 ). In addition, a plurality of balls 8 are arranged on each track 7 (see Figure 1 ).

[0056] The S-shaped groove surface 13 is a groove surface formed by forging on the inner peripheral surface 11a of the nut body 11. The S-shaped groove surface 13 is connected to one end and the other end of the spiral direction of the inner peripheral raceway surface 12. Thus, the ball 8 moving from one end of the raceway 7 to the other end circulates to one end of the raceway 7 using the S-shaped groove surface 13.

[0057] like Figure 2 As shown, there are four inner peripheral track surfaces 12 and four S-shaped groove surfaces 13. Therefore, there are four tracks 7. Hereinafter, the four inner peripheral track surfaces 12 are referred to as the first inner peripheral track surface 12a, the second inner peripheral track surface 12b, the third inner peripheral track surface 12c, and the fourth inner peripheral track surface 12d in order from the first direction X1. In addition, the four S-shaped groove surfaces 13 are referred to as the first S-shaped groove surface 13a, the second S-shaped groove surface 13b, the third S-shaped groove surface 13c in order from the first direction X1 (refer to Figure 3 ), the 4th S-shaped groove surface 13d.

[0058] Figure 3 This is a diagram obtained when the nut of the first embodiment is viewed from the second direction. Figure 3 As shown, when viewed from the second direction X2, the second S-shaped groove surface 13b is arranged to be offset 90 degrees in the right-hand direction relative to the first S-shaped groove surface 13a. When viewed from the second direction X2, the third S-shaped groove surface 13c is arranged to be offset 90 degrees in the right-hand direction relative to the second S-shaped groove surface 13b. When viewed from the second direction X2, the fourth S-shaped groove surface 13d is arranged to be offset 90 degrees in the right-hand direction relative to the third S-shaped groove surface 13c. Thus, the four S-shaped groove surfaces 13 are arranged at intervals of 90 degrees (equal intervals) with the central axis O as the center.

[0059] Here, the first inner peripheral raceway surface 12a of the nut 10 supports the screw shaft 2 from the radially outer side via the balls 8. On the other hand, the first S-shaped groove surface 13a connected to the first inner peripheral raceway surface 12a cannot support the screw shaft 2 via the balls 8. Therefore, the first inner peripheral raceway surface 12a cannot support the screw shaft 2 in the direction in which the first S-shaped groove surface 13a is arranged when viewed from the center axis O (refer to Figure 3 Similarly, the second inner circumferential raceway surface 12b cannot support the direction in which the second S-shaped groove surface 13b is arranged when viewed from the center axis O (refer to Figure 3 The third inner raceway surface 12c cannot support the direction in which the third S-shaped groove surface 13c is arranged when viewed from the center axis O (refer to Figure 3 The fourth inner raceway surface 12d cannot support the direction in which the fourth S-shaped groove surface 13d is arranged when viewed from the center axis O (refer to Figure 3 In the present embodiment, the four S-shaped groove surfaces 13 are dispersed in the circumferential direction, and the ranges that cannot be supported from the radial outer side do not overlap. Therefore, the nut 10 supports the screw shaft 2 from all directions in the circumferential direction.

[0060] Figure 4 This is a stereoscopic view of the nut of Embodiment 1 viewed from the second direction. Figure 4 As shown, the flange 20 is composed of a partial flange 21 protruding radially from the outer peripheral surface 11b of the nut body 11. The partial flange 21 is not formed in an annular shape. In other words, the partial flange 21 extends only in a part of the circumferential direction along the outer peripheral surface 11b of the nut body 11. In addition, the flange 20 of this embodiment has three partial flanges 21. In other words, the flange 20 is composed of three partial flanges 21.

[0061] The three partial flanges 21 are arranged at equal intervals about the central axis O. That is, the three partial flanges 21 are arranged at intervals of 120 degrees. The radially outer surface of the partial flange 21 is provided with a sliding groove surface 22 that is recessed radially inward and open in the axial direction.

[0062] Figure 5 yes Figure 1 The cross-sectional view along the VV line. Figure 5 As shown, the radially outer surface of the partial flange 21 is opposite to the inner surface 101a of the housing 101. The inner surface 101a is provided with three fixing groove surfaces 106 recessed radially outward. The fixing groove surfaces 106 extend in the axial direction (refer to Figure 1 A portion of a cylindrical shaft 107 extending in the axial direction is accommodated inside each fixed groove surface 106 . A portion of the shaft 107 protruding radially inward from the inner surface 101 a of the housing 101 passes through the inner side of the sliding groove surface 22 .

[0063] As described above, when a load in the rotational direction acts on the flange 20, the sliding groove surface 22 is caught on the shaft 107, and the rotation of the flange 20 is restricted. In addition, when an axial load acts on the flange 20, the sliding groove surface 22 slides on the shaft 107 and the nut 10 moves in the axial direction. Therefore, the nut 10 is supported by the housing 101 in a manner that it cannot rotate but can move in the axial direction.

[0064] like Figure 5 As shown, the protrusion 30 protrudes from the second end face 10b of the nut body 11 in the second direction X2. In addition, a stopper 60 is arranged in the second direction X2 of the nut 10. The stopper 60 has an annular female spline portion 61 spline-engaged with the male spline portion 3 and a protrusion 62 protruding radially outward from the female spline portion 61. The stopper 60 does not rotate relative to the screw shaft 2. In other words, the stopper 60 rotates integrally with the screw shaft 2. In addition, when viewed from the second direction X2, the protrusion 62 of the stopper 60 abuts against the protrusion 30 from the right-hand direction.

[0065] Hereinafter, the rotation direction of the screw shaft 2 will be based on the situation viewed from the second direction X2. Figure 5 As shown in FIG. 1 , when the screw shaft 2 rotates in the left-hand direction (counterclockwise direction) when viewed from the second direction X2, this rotation direction is referred to as the first rotation direction L1 (refer to FIG. 1 ). Figure 5 In addition, when the screw shaft 2 rotates in the right-hand direction (clockwise direction) when viewed from the second direction X2, this rotation direction is referred to as the second rotation direction L2 (refer to Figure 5 In addition, when the screw shaft 2 rotates in the first rotation direction L1, the nut 10 moves in the first direction X1.

[0066] The protrusion 30 has a first contact surface 31 on the side facing the first rotation direction L1. The protrusion 62 of the stopper 60 has a second contact surface 63 on the side facing the second rotation direction L2. When the nut 10 is in the initial axial position, the first contact surface 31 of the protrusion 30 abuts against the second contact surface 63 of the stopper 60. Therefore, when the nut 10, which is located closer to the first direction X1 than the initial position, moves in the second direction X2, the protrusion 30 enters the trajectory of the stopper 60 that rotates in the second rotation direction L2 integrally with the screw shaft 2. In addition, the first contact surface 31 of the protrusion 30 contacts the second contact surface 63 of the stopper 60. As a result, the rotation of the screw shaft 2 is restricted, and the nut 10 is arranged in the initial position.

[0067] like Figure 1As shown, the piston 50 has: a pressing portion 51, which is disc-shaped with the central axis O as the center; a cylindrical portion 52, which is cylindrical and extends from the pressing portion 51 in the second direction X2; and a fitting portion 53, which fits with the outer peripheral surface 11b of the nut 10.

[0068] The pressing portion 51 is a portion that presses the liquid in the cylinder 102 in the first direction X1. The pressing portion 51 is disposed inside the cylinder 102 and faces the closing wall 104 of the cylinder 102.

[0069] The inner diameter of the fitting portion 53 is larger than the inner diameter of the cylindrical portion 52. Therefore, a step surface 54 facing the second direction X2 is provided between the inner circumferential surface of the cylindrical portion 52 and the inner circumferential surface of the fitting portion 53. The step surface 54 abuts against the first end surface 10a of the nut 10. In addition, the hydraulic pressure of the liquid in the cylinder 102 acts on the pressing portion 51, and the piston 50 is always pressed in the second direction X2. Therefore, the step surface 54 and the first end surface 10a are always abutted.

[0070] The outer diameters of the cylindrical portion 52 and the fitting portion 53 are slightly smaller than the inner diameter of the cylinder 102. Therefore, a small gap (not shown) is provided between the outer peripheral surface 50a of the piston 50 and the inner peripheral surface 102a of the cylinder 102. Thus, when an axial load acts on the piston 50, the piston 50 is moved in the axial direction while sliding on the inner peripheral surface 102a of the cylinder 102.

[0071] Two sealing members 108 are provided between the piston 50 and the cylinder 102. This prevents the liquid in the cylinder 102 from leaking in the second direction X2 through the small gap between the piston 50 and the cylinder 102.

[0072] As described above, when the nut 10 moves in the first direction X1, the first end surface 10a presses the step surface 54, and the piston 50 moves in the first direction X1. As a result, the hydraulic pressure in the cylinder 102 increases. On the other hand, when the nut 10 moves in the second direction X2, the piston 50 also moves in the second direction X2. As a result, the hydraulic pressure in the cylinder 102 decreases.

[0073] Next, the details of the nut 10 of the first embodiment will be described. Figure 2 As shown, the axial length of the partial flange 21 is shorter than the axial length of the nut body 11. Specifically, the axial length of the partial flange 21 is substantially the same as the axial length M1 of the track 7 (one lead). In addition, the partial flange 21 is disposed at the end of the nut body 11 in the second direction X2.

[0074] like Figure 3As shown, the partial flange 21 has a side surface 21a facing the circumferential direction. A corner portion 26 is provided at the portion where the side surface 21a and the outer peripheral surface 11b of the nut body 11 intersect. In addition, a retreat space 25 is provided between the side surfaces 21a of each partial flange 21. In other words, three retreat spaces 25 are arranged on the outer peripheral side of the nut body 11.

[0075] like Figure 2 As shown in FIG. 1 , the portion of the nut body 11 disposed radially inward of the flange 20 (from Figure 2 The portion of the annular portion 16 that is arranged along the dotted line H1 in the second direction X2 is called the annular portion 16. The annular portion 16 is arranged radially inward of the three partial flanges 21 and the three retreat spaces 25. In addition, a portion of the fourth S-shaped groove surface 13d of the four S-shaped groove surfaces 13 is provided on the inner peripheral surface of the annular portion 16.

[0076] like Figure 3 As shown, the annular portion 16 is divided into three flange connection areas 17 and three flange unconnected areas 18. Figure 3 In the figure, dots are marked to facilitate understanding of the range of the flange unconnected region 18. The flange connected region 17 is a portion of the annular portion 16 where the partial flange 21 is arranged radially outward and connected to the partial flange 21. On the other hand, the flange unconnected region 18 is a portion of the annular portion 16 where the retreat space 25 is arranged radially outward and not connected to the partial flange 21.

[0077] To explain in detail, the flange connection area 17 and the flange non-connected area 18 are distinguished by a virtual straight line H2 connecting the corner 26 and the center axis O as a boundary line. In addition, the flange non-connected area 18 is provided with a retreat space 25 on the radially outer side, and the wall portion of the nut body 11 can be retreated radially outward by forging. In other words, the flange non-connected area 18 is an area where the S-shaped groove surface 13 can be formed by forging. And, in the present embodiment, the fourth S-shaped groove surface 13d is formed on the inner peripheral surface 11a of the flange non-connected area 18 by forging. In this way, according to the present embodiment, it is not necessary to form the S-shaped groove surface 13 in an axially offset manner relative to the flange 20. Therefore, it is possible to avoid enlarging the nut 10 in the axial direction.

[0078] The fourth S-shaped groove surface 13d among the four S-shaped groove surfaces 13 is arranged at a position closest to the protrusion 30 in the axial direction (see Figure 2). The 4th S-shaped groove surface 13d and the protrusion 30 are arranged 180 degrees apart in the circumferential direction. Therefore, even if the contact load generated by the stopper 60 acts on the protrusion 30, the 4th S-shaped groove surface 13d will not be deformed. In other words, the ball 8 continues to roll smoothly on the 4th S-shaped groove surface 13d. In addition, it is also possible to avoid the protrusion 30 being deformed due to the load when forging the inner peripheral surface 11a of the nut body 11. In other words, it is also possible to avoid the initial position deviation.

[0079] In summary, the ball screw device 1 of the first embodiment includes a screw shaft 2, a nut 10, and a plurality of balls 8 arranged between the screw shaft 2 and the nut 10. The nut 10 includes: a nut body 11, which is cylindrical and is penetrated by the screw shaft 2; a plurality of inner circumferential raceway surfaces 12 and a plurality of S-shaped groove surfaces 13, which are recessed radially outward from the inner circumferential surface 11a of the nut body 11; and a flange 20, which protrudes radially outward from the outer circumferential surface 11b of the nut body 11. The flange 20 is composed of at least one or more partial flanges 21 extending only in a part of the circumferential direction along the outer circumferential surface 11b of the nut body 11. When there is one partial flange 21, the space between one end and the other end of the partial flange 21 in the circumferential direction is a retreat space 25 for retreating the wall portion of the nut body 11, and when there are two or more partial flanges 21, the space between the circumferentially adjacent partial flanges 21 is a retreat space 25 for retreating the wall portion of the nut body 11. One of the plurality of S-shaped groove surfaces 13 (the fourth S-shaped groove surface 13 d ) is arranged radially inside the retreat space 25 .

[0080] According to the first embodiment, the nut 10 is prevented from being enlarged in the axial direction. In addition, the nut 10 is made lighter than when the flange 20 is annular.

[0081] Furthermore, in Embodiment 1, the plurality of S-shaped groove surfaces 13 are arranged at equal intervals in the circumferential direction.

[0082] The range in which the screw shaft 2 cannot be supported from the radially outer side is dispersed in the circumferential direction. Therefore, the nut 10 can support the screw shaft 2 from all directions in the circumferential direction.

[0083] Furthermore, in the first embodiment, the flange 20 has two or more partial flanges 21 arranged at equal intervals in the circumferential direction.

[0084] In Embodiment 1, the shaft 107 supported by the housing 101 and extending axially parallel to the screw shaft 2 is arranged radially outside the partial flange 21. The outer peripheral surface of the partial flange 21 is provided with a sliding groove surface 22 that is recessed radially inward and accommodates the shaft therein.

[0085] Thus, the nut 10 is supported by the housing 101 in a manner that is non-rotatable and movably axially.

[0086] Furthermore, in Embodiment 1, a protrusion 30 is provided on one end face (the second end face 10b) of the nut body 11, which protrudes in the axial direction and contacts the stopper 60 that does not rotate relative to the screw shaft 2. The S-shaped groove surface 13 (the fourth S-shaped groove surface 13d) that is arranged closest to the protrusion in the axial direction among the plurality of S-shaped groove surfaces 13 is arranged to be offset in the circumferential direction relative to the protrusion 30.

[0087] According to the above structure, the fourth S-shaped groove surface 13d is separated from the protrusion 30. Therefore, even if a contact load with the stopper 60 acts on the protrusion 30, the fourth S-shaped groove surface 13d is not deformed.

[0088] Embodiment 1 is described above, but the present disclosure is not limited to the example shown in Embodiment 1. For example, in the embodiment, the 4th S-shaped groove surface 13d and the protrusion 30 are arranged at an interval of 180 degrees, but the present disclosure is not limited to this. As long as the 4th S-shaped groove surface 13d and the protrusion 30 do not overlap when viewed from the axial direction, for example, the 4th S-shaped groove surface 13d and the protrusion 30 may be arranged at an interval of about 30 degrees. In addition, the present disclosure may also be a nut 10 without the protrusion 30. In addition, in the embodiment, an example of providing a sliding groove surface 22 on the outer peripheral surface of the partial flange 21 in order to achieve the anti-rotation of the nut 10 is given, but the present disclosure is not limited to this. For example, the partial flange 21 itself may enter the fixed groove surface 106. Alternatively, a protrusion may be provided on the outer peripheral surface of the partial flange 21, and the protrusion may enter the fixed groove surface 106 of the housing 101. The protrusion provided on the outer peripheral surface of the partial flange 21 may be provided integrally with the partial flange 21 or may be provided independently (a member independent of the partial flange 21 ).

[0089] Next, a description will be given of Modification 1 and Modification 2 in which the nut 10 of Embodiment 1 is modified. Hereinafter, only the modified points will be described.

[0090] (Variant 1)

[0091] Figure 6 This is a view obtained when the nut of modification example 1 is viewed from the second direction. The nut 10A of modification example 1 is different from the nut 10 of embodiment 1 in that the nut 10A has a flange 20A instead of the flange 20. The flange 20A has a partial flange 21A. Therefore, there is only one space (retreat space 25A) between one end 21b and the other end 21c of the partial flange 21A in the circumferential direction. Similarly, the annular portion 16A is divided into a flange connection area 17A and a flange unconnected area 18A. In addition, a fourth S-shaped groove surface 13d is provided in the flange unconnected area 18A that can be forged.

[0092] The length of the partial flange 21A in the circumferential direction is longer than that of the partial flange 21 of the first embodiment. Specifically, the angle θ from one end 21b to the other end 21c of the partial flange 21A is about 300 degrees. Three sliding groove surfaces 22 are provided on the outer circumferential surface of the partial flange 21A. According to the partial flange 21A, the rigidity is high and it is not easy to deform compared with the partial flange 21 of the first embodiment. Therefore, it is avoided that the partial flange 21A is deformed and the sliding property between the shaft 107 is impaired.

[0093] Modification 1 has been described above, but as shown in Modification 1, the present disclosure is not particularly limited with respect to the circumferential length of the partial flange and the number of the partial flanges.

[0094] (Variant 2)

[0095] Figure 7 This is a view of the flange unconnected area of ​​the nut of Modification 2 viewed from the second direction. Figure 7 As shown, the nut 10B of the second modification is different from the nut 10 of the first embodiment in that a part of the fourth S-shaped groove surface 13 d is provided in the flange connection region 17B.

[0096] To explain in detail, the central portion of the S-shaped groove surface 13 in the length direction is the bottom surface 14a that is most recessed radially outward. The two ends of the S-shaped groove surface 13 in the length direction are inclined surfaces 14b and 14c whose recess gradually increases as they approach the bottom surface 14a. In addition, the length direction of the S-shaped groove surface 13 refers to the direction along the S-shaped groove surface 13, also referred to as the direction along the shape of the letter S. In addition, during forging, the amount of wall portion that retreats radially outward due to the forming of the bottom surface 14a is relatively large. On the other hand, the amount of wall portion that retreats radially outward due to the forming of the inclined surfaces 14b and 14c is less than that of the bottom surface 14a. In variant example 2, a portion of the inclined surfaces 14b and 14c in the S-shaped groove surface 13 (the portion that is continuous with the inner peripheral track surface 12) is provided in the flange connection area 17B. Furthermore, the remaining portions of the inclined surfaces 14 b and 14 c (portions continuous with the bottom surface 14 a ) and the bottom surface 14 a are provided in the flange unconnected region 18B (radially inward of the retreat space 25B).

[0097] To repeat, if the flange 20B (partial flange 21B) is arranged on the radially outer side, most of the wall portion of the nut body 11 cannot be retreated to the radially outer side by forging. That is, since it is difficult to form the bottom surface 14a, the entire S-shaped groove surface 13 is not formed on the radially inner side of the flange 20 (partial flange 21) in the past. On the other hand, even when the flange 20 (partial flange 21) is arranged on the radially outer side, as long as a small amount of wall portion is retreated to the radially outer side. In other words, even the inner peripheral surface 11a of the flange connection area 17B can be formed by forging as long as it is a part of the inclined surface 14b, 14c with a small amount of depression.

[0098] In the present disclosure, when a part of the inclined surfaces 14b and 14c can be formed by forging relative to the flange connection area 17B, it is also possible to form them as shown in Modification 2. In other words, the present disclosure does not limit the entire S-shaped groove surface 13 to be formed in the flange non-connected area 18B as shown in Modification 2, and the layout of the S-shaped groove surface 13 has a high degree of freedom.

[0099] In addition, the groove surface (inclined surface 14b, 14c) that can be formed in the flange connection area 17B is limited to a maximum recess amount N (refer to Figure 7 ) is a groove surface with a depression amount of less than 50%, preferably a groove surface with a depression amount of less than 20%.

[0100] (Variant 3)

[0101] Figure 8 This is a perspective view of the nut of Modification 3 viewed from the second direction. Fig. 9 This is a diagram when the nut of Modification 3 is viewed from the second direction. Fig.10 It is magnified Fig. 9 In addition, Figure 8 As shown, in modification example 3, an example is given in which the second end face 10b of the nut 10E protrudes in the second direction X2 more than the flange 20E (partial flange 21E). That is, the flange 20E (partial flange 21E) of modification example 3 is arranged at a position slightly closer to the first direction X1 than the end of the nut body 11 in the second direction X2. However, the present disclosure may also be such that the flange 20E is arranged at the end of the nut body 11 in the second direction X2. In addition, the sliding groove surfaces 22 of modification example 3 are not arranged at equal intervals in the circumferential direction, but the present disclosure may also be such that the sliding groove surfaces 22 are arranged at equal intervals in the circumferential direction.

[0102] like Figure 8 , Fig. 9 As shown, the flange 20E of the nut 10E of the modification example 3 is different from the partial flange 21A of the modification example 1 (see Figure 6That is, there is only one retreat space 25E in Modification 3.

[0103] On the other hand, Fig. 9 As shown in FIG. 1 , the partial flange 21E of the modification example 3 is in the shape of the letter D when viewed from the axial direction, which is different from the partial flange of the modification example 1. That is, in the partial flange 21E of the modification example 3, the side surface 121b located at the one end 21b in the circumferential direction and the side surface 121c located at the other end 21c in the circumferential direction are connected in a straight line. Therefore, the retreat space 25E of the modification example 3 is a space extending in the circumferential direction between the one end 21b and the other end 21c of the partial flange 21E. Hereinafter, the straight side surface formed by combining the side surface 121b and the side surface 121c is referred to as the straight side surface 121.

[0104] When viewed from the axial direction, the straight side surface 121 is a tangent line to the outer peripheral surface 11b of the nut body 11 (annular portion 16). Hereinafter, a virtual straight line connecting the tangent point P121 between the straight side surface 121 and the outer peripheral surface 11b and the central axis O when viewed from the axial direction is referred to as a virtual line H121.

[0105] The distance H3 between the outer peripheral surface 11b of the annular portion 16 and the straight side surface 121 decreases as the contact point P121 is approached. In other words, the radial thickness of the portion of the partial flange 21E provided with the straight side surface 121 decreases as the contact point P121 is approached. In addition, in the modification 3, the radial thickness of the partial flange 21E is H4. Hereinafter, the portion of the partial flange 21E whose radial thickness is less than 1 / 2 of H4 is referred to as the incomplete flange 121E (refer to Fig. 9 of the range filled by points).

[0106] like Fig.10 As shown, in Modification 3, the flange unconnected region 18 (a portion of the annular portion 16 where the escape space 25 is arranged radially outward and not connected to the partial flange 21 ) is a portion of the annular portion 16 that overlaps with the virtual line H121 .

[0107] In the third modification, the fourth S-shaped groove surface 13d of the four S-shaped groove surfaces 13 is arranged in the annular portion 16. And the bottom surface 14a of the fourth S-shaped groove surface 13d, which is most deeply recessed toward the radial outside, is arranged in the flange unconnected region 18. Therefore, for the bottom surface 14a of the fourth S-shaped groove surface 13d, most of the wall portion of the nut body 11 can be retracted toward the radial outside by forging.

[0108] On the other hand, the inclined surfaces 14b and 14c of the fourth S-shaped groove surface 13d are arranged in the flange connection area 17. However, the portion arranged radially outside the flange connection area 17 is an incomplete flange 121E having a small radial thickness. Therefore, the wall portion used to form the inclined surfaces 14b and 14c can be retreated radially outward. Based on the above, the fourth S-shaped groove surface 13d can be formed by forging.

[0109] In the third modification, the straight side surface 121 is a tangent to the outer peripheral surface 11b of the annular portion 16. However, the present disclosure may also allow the straight side surface 121 not to be a tangent to the outer peripheral surface 11b of the annular portion 16. In other words, the straight side surface 121 may be arranged radially outward of the outer peripheral surface 11b of the annular portion 16, and the straight side surface 121 and the outer peripheral surface 11b may have no intersection (see Fig.12 In this case, the annular portion 16 does not have the flange unconnected region 18, and the entirety is only the flange connected region 17. However, if the portion disposed radially outside the S-shaped groove surface 13 is an incomplete flange 121E, the S-shaped groove surface 13 can be formed by forging.

[0110] In addition, in addition to the case where the straight side surface 121 and the outer peripheral surface 11b have no intersection, the present disclosure may also be that the straight side surface 121 and the outer peripheral surface 11b of the annular portion 16 have two intersections. In other words, the straight side surface 121 may be a part of the outer peripheral surface 11b of the annular portion 16 cut off, and the shape of the outer peripheral surface 11b of the annular portion 16 is the letter D when viewed from the axial direction.

[0111] In addition, in the third modification, the end of the length direction of the S-shaped groove surface 13 (the entrance and exit of the S-shaped groove surface 13) is arranged on the radial inner side of the incomplete flange 121E, but the present disclosure may also be that the end of the length direction of the S-shaped groove surface 13 is not arranged on the radial inner side of the incomplete flange 121E. This is because, as described in the second modification, as long as the maximum depression amount N relative to the bottom surface 14a (refer to Figure 7 ) is a groove surface with a recess amount of 50% or less, it can be formed even if it is arranged on the radial inner side of the partial flange 20E (excluding the range of the incomplete flange 121E).

[0112] In addition, in Modification 3, an example of a partial flange having one straight side surface 121 is given, but the present disclosure may also be that the partial flange has two straight side surface portions 121, and the two straight side surface portions 121 are parallel to each other. In other words, the present disclosure may also be a partial flange having a plurality of straight side surfaces 121. In addition, the partial flange of Modification 3 is provided with a sliding groove surface 22 and used as a rotation stop portion, but the present disclosure may also use it for other purposes.

[0113] Embodiment 1 and its modified examples are described above. Here, the partial flanges of Embodiment 1 and the modified examples are used as the rotation stopper of the nut, but the present disclosure is not limited to this. Next, an example of using the partial flange for purposes other than the rotation stopper is described.

[0114] (Implementation Method 2)

[0115] Fig.11 This is a stereoscopic view of the nut of Embodiment 2 viewed from the second direction. Fig.11 As shown, in the second embodiment, the flange 20C of the nut 10C has three partial flanges 21C, which is the same as the first embodiment. On the other hand, the partial flange 21C is not provided with a sliding groove surface 22 penetrated by the shaft 107, which is different from the partial flange 21 of the first embodiment. In addition, the partial flange 21C is provided with a through hole 24 penetrating in the axial direction, which is different from the partial flange 21 of the first embodiment.

[0116] In the second embodiment, the nut 10C is arranged to be axially opposed to the planetary gear 114 of the planetary gear mechanism 110. Figure 1 ) is inserted into the through hole 24 of the partial flange 21C. Therefore, the rotational motion of the planetary gear 114 rotating (revolving) around the central axis O is input to the three partial flanges 21C, causing the nut 10C to rotate. Based on the above, the three partial flanges 21C of the second embodiment serve as the planetary carrier 116 of the planetary gear mechanism 110 (see Figure 1 ) is used. Furthermore, according to this second embodiment, the planetary carrier 116 (see Figure 1 ), achieving a reduction in the number of components. In addition, in embodiment 2, the nut 10C rotates and the screw shaft 2 moves axially. In addition, in this embodiment, the hole provided in the local flange 21C is a through hole 24, but it can also be a blind hole (a non-through hole).

[0117] In the second embodiment, the through hole 24 is applied to the nut 10C having a plurality of (three) partial flanges 21C, but the present disclosure is not limited thereto. For example, the nut 10A having the partial flange 21A shown in the first modification may be provided with the through hole 24. Fig.12 This is a diagram obtained when the nut of Modification Example 4 is viewed from the second direction. Fig.12 As shown, the flange 20F of the nut 10F of Modification 4 is a D-shaped partial flange 21F having an incomplete flange 121E as shown in Modification 3. In the present disclosure, the D-shaped partial flange 21F may be provided with a through hole 24.

[0118] (Implementation 3)

[0119] Fig.13 This is a perspective view of the nut according to the third embodiment when viewed from the second direction. Fig.14 This is a diagram obtained when the nut of the third embodiment is viewed from the second direction. Fig.13 As shown, the nut 10D of the third embodiment is different from the nut 10 of the first embodiment in that the two partial flanges 21D are provided. The two partial flanges 21D are arranged to be point-symmetrical about the central axis O. That is, the two partial flanges 21D are arranged to be staggered 180 degrees in the circumferential direction. Therefore, in the third embodiment, two retreat spaces 25D are provided.

[0120] The axial length of the partial flange 21D is the same as the axial length of the nut body 11. Fig.14 As shown in FIG. 1 , the nut 10D is inserted into the inner peripheral side of the driven pulley 200. In addition, the partial flange 21D is engaged with the groove 220 provided on the inner peripheral surface 210 of the driven pulley 200. When the belt 230 transmits power to the driven pulley 200, the nut 10D rotates integrally with the driven pulley 200, and the screw shaft 2 (see FIG. 1 ) rotates. Figure 1 ) moves in the axial direction. As described above, the two partial flanges 21D of the third embodiment are used as the rotation-stopping portion for restricting the relative rotation with respect to the driven pulley 200.

[0121] Furthermore, in the third embodiment, the entire axial direction of the nut body 11 is the annular portion 16. In other words, all of the four S-shaped groove surfaces 13 are arranged radially inward of the two partial flanges 21D and the two escape spaces 25D.

[0122] like Fig.14 As shown, the annular portion 16 is divided into two flange connection areas 17D and two flange non-connected areas 18D. The four S-shaped groove surfaces 13 (the first S-shaped groove surface 13a, the second S-shaped groove surface 13b, the third S-shaped groove surface 13c, and the fourth S-shaped groove surface 13d) are arranged at 90-degree intervals as in the first embodiment. Moreover, all four S-shaped groove surfaces 13 are arranged on the inner circumferential surface 11a of the flange non-connected area 18D. In such a third embodiment, it is also unnecessary to form the S-shaped groove surface 13 offset in the axial direction relative to the flange 20D (partial flange 21D). Therefore, it is possible to avoid enlarging the nut 10 in the axial direction.

[0123] In addition, regarding the number of S-shaped groove surfaces 13 arranged on the radial inner side of the retreat space 25, in the first embodiment, it is one of the four S-shaped groove surfaces 13, and in the third embodiment, it is all of the four S-shaped groove surfaces 13, but the present disclosure may also be two or three of the plurality of (four) S-shaped groove surfaces 13. That is, for the present disclosure, as long as at least one of the plurality of S-shaped groove surfaces 13 is arranged on the radial inner side of the retreat space 25, it is not limited to the example shown in the embodiment.

[0124] The embodiments and modifications are described above, but in the present disclosure, the outer diameter of the nut body 11 may be different from the outer diameter of the annular portion 16. In other words, the outer diameter of the annular portion 16 may be larger or smaller than the outer diameter of the nut body 11.

[0125] In addition, the present disclosure may be a combination of the following structures.

[0126] (1) A nut, wherein:

[0127] The nut has:

[0128] The nut body is cylindrical and the screw shaft passes through it;

[0129] a plurality of inner peripheral track surfaces and a plurality of S-shaped groove surfaces, which are recessed radially outward from the inner peripheral surface of the nut body; and

[0130] a flange protruding radially outward from the outer peripheral surface of the nut body,

[0131] The flange has at least one partial flange, and the partial flange extends only in a portion of the circumference along the outer peripheral surface of the nut body.

[0132] When there is one partial flange, the space between one end and the other end of the partial flange in the circumferential direction is a retreat space for the wall portion of the nut body to retreat. When there are two or more partial flanges, the space between the partial flanges adjacent to each other in the circumferential direction is a retreat space for the wall portion of the nut body to retreat.

[0133] One of the plurality of S-shaped groove surfaces is arranged radially inside the retreat space.

[0134] (2) The nut according to (1), wherein:

[0135] The plurality of S-shaped groove surfaces are arranged at equal intervals in the circumferential direction.

[0136] (3) The nut according to (1) or (2), wherein:

[0137] The flange includes two or more partial flanges arranged at equal intervals in the circumferential direction.

[0138] (4) The nut according to any one of (1) to (3), wherein

[0139] A shaft supported by the housing and extending in an axial direction parallel to the screw shaft is arranged radially outside the partial flange.

[0140] The outer peripheral surface of the partial flange is provided with a sliding groove surface which is recessed radially inward and accommodates the shaft therein.

[0141] (5) The nut according to any one of (1) to (3), wherein

[0142] The planetary gears of the planetary gear mechanism and the partial flange are opposite to each other in an axial direction parallel to the screw shaft.

[0143] The partial flange is provided with a hole for inserting a transmission shaft supporting the planetary gear.

[0144] (6) The nut according to any one of (1) to (3), wherein

[0145] The nut body is arranged inside the driven pulley.

[0146] The partial flange is inserted into a groove provided on the inner peripheral surface of the driven pulley.

[0147] (7) The nut according to any one of (1) to (6), wherein

[0148] A protrusion is provided on one end surface of the nut body, the protrusion protruding in the axial direction and contacting a stopper that does not rotate relative to the screw shaft.

[0149] The S-shaped groove surface, which is disposed closest to the protrusion in the axial direction among the plurality of S-shaped groove surfaces, is disposed offset in the circumferential direction with respect to the protrusion.

[0150] (8) A ball screw device, wherein:

[0151] The ball screw device has:

[0152] Screw shaft;

[0153] The nut according to any one of (1) to (7); and

[0154] A plurality of balls are arranged between the screw shaft and the nut.

[0155] Description of Reference Numerals

[0156] 1. Ball screw device; 2. Screw shaft; 4. Screw shaft body; 5. Outer peripheral track surface; 7. Track; 8. Ball; 10, 10B, 10C, 10D, 10E, 10F, Nut; 11. Nut body; 12. Inner peripheral track surface; 13. S-shaped groove surface; 14a, bottom surface; 14b, 14c, inclined surface; 16, annular portion; 17, 17A, 17B, flange connection area; 18, 18A, 18B, flange unconnected area; 20, 20A, 20B, 20C, 2 0D, flange; 21, 21A, 21B, 21C, 21D, partial flange; 22, sliding groove surface; 24, through hole (hole); 25, 25A, 25B, 25D, retreat space; 26, corner; 30, protrusion; 31, first contact surface; 50, piston; 60, stopper; 63, second contact surface; 100, electric actuator; 101, housing; 102, cylinder; 110, planetary gear mechanism; 121, incomplete flange; 200, driven pulley; 230, belt.

Claims

1. A nut, wherein: The nut has: The nut body is cylindrical and the screw shaft passes through it; a plurality of inner peripheral track surfaces and a plurality of S-shaped groove surfaces, which are recessed radially outward from the inner peripheral surface of the nut body; and a flange protruding radially outward from the outer peripheral surface of the nut body, The flange is composed of at least one partial flange, and the partial flange extends only in a part of the circumferential direction along the outer peripheral surface of the nut body. When there is one partial flange, the space between one end and the other end of the partial flange in the circumferential direction is a retreat space for the wall portion of the nut body to retreat. When there are two or more partial flanges, the space between the partial flanges adjacent to each other in the circumferential direction is a retreat space for the wall portion of the nut body to retreat. One of the plurality of S-shaped groove surfaces is arranged radially inside the retreat space.

2. The nut according to claim 1, wherein: The plurality of S-shaped groove surfaces are arranged at equal intervals in the circumferential direction.

3. The nut according to claim 1, wherein: The flange includes two or more partial flanges arranged at equal intervals in the circumferential direction.

4. The nut according to any one of claims 1 to 3, wherein A shaft supported by the housing and extending in an axial direction parallel to the screw shaft is arranged radially outside the partial flange. The outer peripheral surface of the partial flange is provided with a sliding groove surface which is recessed radially inward and accommodates the shaft therein.

5. The nut according to any one of claims 1 to 3, wherein The planetary gears of the planetary gear mechanism and the partial flange are opposite to each other in an axial direction parallel to the screw shaft. The partial flange is provided with a hole for inserting a transmission shaft supporting the planetary gear.

6. The nut according to any one of claims 1 to 3, wherein: The nut body is arranged inside the driven pulley. The partial flange is inserted into a groove provided on the inner peripheral surface of the driven pulley.

7. The nut according to any one of claims 1 to 6, wherein: A protrusion is provided on one end surface of the nut body, the protrusion protruding in the axial direction and contacting a stopper that does not rotate relative to the screw shaft. The S-shaped groove surface, which is disposed closest to the protrusion in the axial direction among the plurality of S-shaped groove surfaces, is disposed offset in the circumferential direction with respect to the protrusion.

8. A ball screw device, wherein: The ball screw device has: Screw shaft; The nut according to any one of claims 1 to 7; and A plurality of balls are arranged between the screw shaft and the nut.

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