Ball screw device

Abstract

To provide a ball screw device for suppressing damage on a circulation component.SOLUTION: A circulation component of a ball screw device includes: a body having a first opening and a second opening; and a connection part for picking a ball in a tangential direction and guiding the ball to the first opening and the second opening. The connection part includes: a center wall part extending from an area between the first opening and the second opening toward an end part of a first thread; a first side wall part provided on one side of an axial direction with respect to the center wall part; and a second side wall part provided on the other side of the axial direction with respect to the center wall part. A part closer to an end part of the first thread at the center wall part, there are provided: a first picking part for picking a ball at a radially inner side from a center of the ball and from the other side of the axial direction from the center of the ball; and a second picking part for picking a ball at a radially inner side from a center of the ball and from the one side of the axial direction from the center of the ball. The first picking part extends to the first opening, and the second picking part extends to the second opening.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] As shown in Patent Document 1, as one type of ball screw device, there is a ball screw device having two raceways. Further, in the ball screw device of Patent Document 1, preload is applied to the balls. Specifically, in the screw shaft of Patent Document 1, one thread between the two raceways is cut away. The nut also has one thread between the two raceways cut away. And the thread of the screw shaft and the thread of the nut are arranged with an axial displacement corresponding to one raceway. That is, the space between the thread of the screw shaft and the thread of the nut forms the raceway. Furthermore, the distance between the thread of the screw shaft and the thread of the nut is smaller than the diameter of the ball. As a result, the balls are clamped between the thread of the screw shaft and the thread of the nut, and preload is applied to the balls.

[0003] The ball screw device includes a circulation component for circulating the balls. The circulation component has a lifting portion (tang) that protrudes toward the groove bottom of the screw shaft. When the ball contacts the lifting portion, the ball is lifted from the groove bottom of the screw shaft, and the ball enters the circulation path of the circulation component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The conventional scooping-up part has a pointed tip shape. Also, in order to avoid contact with the groove bottom of the screw shaft, a gap is provided between the conventional scooping-up part and the groove bottom of the screw shaft. Therefore, if the ball is scooped up poorly, the ball may fall into (be pinched by) the gap between the scooping-up part and the groove bottom of the screw shaft. If the ball falls into the gap, the scooping-up part (circulating part) will be damaged. From the above, for a ball screw device having two raceways, it is desired to develop a ball screw device capable of suppressing damage to the scooping-up part (circulating part).

[0006] The present disclosure has been made in view of the above problems, and an object thereof is to provide a ball screw device that suppresses damage to a circulating part.

Means for Solving the Problems

[0007] To achieve the above object, a ball screw device according to an aspect of the present disclosure includes a nut having a first thread on its inner peripheral surface, a screw shaft having a second thread on its outer peripheral surface, a plurality of balls disposed in an orbital path between the nut and the screw shaft, and a circulation component fixed to the nut and provided with a first circulation path and a second circulation path. The first thread and the second thread are arranged offset in the axial direction parallel to the axis of the screw shaft. The nut is formed by recessing the inner peripheral surface radially outward and has a housing portion for housing the circulation component. The first thread has an end portion cut out by the housing portion. The circulation component is an entrance and exit of the first circulation path and the second circulation path, and includes a main body portion provided with a first opening portion and a second opening portion that open toward the end portion of the first thread, and a connection portion that extends from the main body portion toward the end portion of the first thread and scoops up the balls in the tangential direction and guides them to the first opening portion and the second opening portion. The connection portion includes a central wall portion that extends from between the first opening portion and the second opening portion to the end portion of the first thread, a first side wall portion that is disposed on one side of the central wall portion in the axial direction and extends while facing the second thread in the radial direction, and a second side wall portion that is disposed on the other side of the central wall portion in the axial direction and extends while facing the second thread in the radial direction. At a portion of the central wall portion near the end portion of the first thread, a first scooping portion that bulges from one axial side surface of the central wall portion, scoops up the ball radially inside the center of the ball, and scoops up the ball from the other side in the axial direction of the center of the ball, and a second scooping portion that bulges from the other axial side surface of the central wall portion, scoops up the ball radially inside the center of the ball, and scoops up the ball from one side in the axial direction of the center of the ball are provided. The first scooping portion extends along the central wall portion to the first opening portion. The second scooping portion extends along the central wall portion to the second opening portion.

[0008] According to the present disclosure, a ball that has moved from the raceway to the first connection path (between the central wall portion and the first side wall portion) rides up (is lifted up) on a first lifting portion that is radially inward of the center of the ball. Further, the ball is lifted up to the first lifting portion from the other axial direction with respect to the center of the ball. Thus, the ball is displaced in one axial direction and abuts against the first side wall portion. Then, the ball moves to the first opening while being supported by the two surfaces of the first lifting portion and the first side wall portion. Similarly, a ball that has moved from the raceway to the second connection path (between the central wall portion and the second side wall portion) also moves to the second opening while being supported by the two surfaces of the second lifting portion and the second side wall portion. From the above, according to the present disclosure, the ball can be reliably lifted up by the lifting portion. Thus, it is possible to avoid the ball falling between the lifting portion and the groove bottom of the screw shaft.

Effect of the Invention

[0009] According to the ball screw device of the present disclosure, damage to the circulating component is suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by the following embodiments for carrying out the invention (hereinafter referred to as embodiments). In addition, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, substantially the same ones, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

[0012] FIG. 1 is a cross-sectional view obtained by axially cutting the central portion in the axial direction of the ball screw device according to the embodiment. FIG. 2 is an enlarged view of the first thread and the second thread and the vicinity thereof shown in FIG. 1. FIG. 3 is a view of the nut as viewed from the first direction. FIG. 4 is a cross-sectional view obtained by axially cutting the end portion in the first direction of the ball screw device according to the embodiment. FIG. 5 is a schematic diagram showing the movement path of the balls (the relationship between the rolling path, the return path, and the circulation path) in the embodiment. FIG. 6 is an enlarged view of the vicinity of the first opening and the second opening in FIG. 4. FIG. 7 is a cross-sectional view taken along the arrow VII-VII line in FIG. 4. FIG. 8 is a cross-sectional view taken along the arrow VIII-VIII line in FIG. 6. FIG. 9 is a cross-sectional view taken along the arrow IX-IX line in FIG. 6. FIG. 10 is a cross-sectional view taken along the arrow X-X line in FIG. 6.

[0013] As shown in FIG. 1, the ball screw device 100 includes a nut 1, a screw shaft 2, a plurality of balls 3, and a circulation component 4 (not shown in FIG. 1; refer to FIGS. 4 and 5).

[0014] As shown in FIG. 2, the nut 1 includes a cylindrical nut body 10 and a first thread 11 provided on the inner peripheral surface of the nut body 10. Hereinafter, the direction parallel to the axis X of the screw shaft 2 is referred to as the axial direction. The direction in which the first thread 11 extends is referred to as the spiral direction.

[0015] The first thread 11 has a first side surface 12 facing one axial direction and a second side surface 13 facing the other axial direction. The first side surface 12 and the second side surface 13 form an R shape and serve as the raceways on which the balls 3 roll. The radius of curvature of the first side surface 12 and the second side surface 13 is larger than the radius of curvature of the balls 3, and the contact with the balls 3 is at one point (in FIG. 2, since the shapes of the first side surface 12 and the second side surface 13 are simplified, it is a surface contact). Hereinafter, the direction in which the first side surface 12 faces among the axial directions is referred to as the first direction X1. The direction in which the second side surface 13 faces is referred to as the second direction X2.

[0016] Between the first threads 11 on the inner peripheral surface of the nut body 10, there is a groove bottom 14. The nut body 10 is provided with a first return path 15 and a second return path 16 penetrating in the axial direction.

[0017] The screw shaft 2 is a solid shaft member. A second thread 5 is provided on the outer peripheral surface of the screw shaft 2. The second thread 5 has a first side surface 6 facing the first direction X1 and a second side surface 7 facing the second direction X2. The first side surface 6 and the second side surface 7 form an R shape and serve as the raceways on which the balls 3 roll. The radius of curvature of the first side surface 6 and the second side surface 7 is larger than the radius of curvature of the balls 3, and the contact with the balls 3 is at one point (in FIG. 2, since the shapes of the first side surface 6 and the second side surface 7 are simplified, it is a surface contact). Between the second threads 5 on the outer peripheral surface of the screw shaft 2, there is a groove bottom 8.

[0018] The raceways of the ball screw device 100 consist of two, namely, a first raceway L1 and a second raceway L2. Specifically, the first thread 11 and the second thread 5 are arranged offset in the axial direction. And the space between the first side surface 12 of the first thread 11 and the second side surface 7 of the second thread 5 is the first raceway L1. Also, the space between the second side surface 13 of the first thread 11 and the first side surface 6 of the second thread 5 is the second raceway L2.

[0019] The distance between one side surface 12 of the first thread 11 and the other side surface 7 of the second thread 5 is slightly smaller than the diameter of the ball 3. Therefore, each ball 3 arranged on the first track L1 and the second track L2 is preloaded by the one side surface 12 and the other side surface 7 as shown by the arrows F1 and F2 in Fig. 2. Thus, the ball 3 makes two-point contact between the first thread 11 and the second thread 5, and the behavior of the ball screw device 100 becomes stable. Note that the ball 3 on the first track L1 and the ball 3 on the second track L2 are in a back-to-back combination.

[0020] As shown in Fig. 3, a housing portion 20 is provided on the end face 17 of the nut body 10. This housing portion 20 is a space for housing the circulating component 4 (see Fig. 4). The circulating component 4 is provided at both ends of the nut 1 (see Fig. 5). Therefore, the housing portion 20 is provided at each of both ends of the nut body 10. Hereinafter, the housing portion 20 and the circulating component 4 provided at the end in the first direction X1 will be described, and the housing portion 20 and the circulating component 4 provided at the end in the second direction X2 will be omitted.

[0021] The housing portion 20 notches the inner peripheral surface and the end face 17 of the nut body 10. Further, the housing portion 20 is open to the inner peripheral surface of the nut body 10. Also, the first thread 11 and the groove bottom 14 arranged on the inner peripheral side of the nut body 10 are notched by the housing portion 20. The nut body 10 has an outer side surface 21 surrounding the outer peripheral side of the housing portion 20 and a bottom surface 22 arranged in the second direction X2 with respect to the housing portion 20. Openings of the first return path 15 and the second return path 16 are provided on the bottom surface 22. Further, the end portion 11a of the first thread 11 notched by the housing portion 20 is arc-shaped.

[0022] As shown in Fig. 4, the circulating component 4 is an end deflector. In the present disclosure, the material of the circulating component 4 is not particularly limited. The circulating component 4 includes a main body portion 40 housed in the housing portion 20 and a connecting portion 50 extending from the main body portion 40 to the inner peripheral side of the nut body 10.

[0023] The main body portion 40 has a first contact surface 41 that abuts against the outer surface 21 of the housing portion 20 and a second contact surface 42 that abuts against the bottom surface 22. A first circulation path M and a second circulation path N are provided in the main body portion 40. The groove widths H1 and H2 of the first circulation path M and the second circulation path N are slightly larger than the diameter of the ball 3. Therefore, a gap is formed between the first circulation path M and the second circulation path N and the rolling ball 3. Note that the gap between the first circulation path M and the second circulation path N and the ball 3 absorbs the manufacturing errors generated in the circulation component 4.

[0024] The first circulation path M has a first circumferential groove M1 extending in the circumferential direction and a first axial groove M2 extending in the axial direction. The second circulation path N has a second circumferential groove N1 extending in the circumferential direction and a second axial groove N2 extending in the axial direction. The first circumferential groove M1 and the second circumferential groove N1 extend in the spiral direction.

[0025] The internal spaces of the first circulation path M and the second circulation path N are open to the first contact surface 41. In other words, the portions where a part of the first contact surface 41 is recessed are the first circulation path M and the second circulation path N. The portions of the first circulation path M and the second circulation path N that are open from the first contact surface 41 are covered by the outer surface 21 of the nut 1 (see FIGS. 7 to 10).

[0026] One end of the first circulation path M is provided with an opening at the second contact surface 42 and is connected to the opening of the second return path 16 (see FIG. 3). One end of the second circulation path N is provided with an opening at the second contact surface 42 and is connected to the opening of the first return path 15 (see FIG. 3).

[0027] A first opening M3 that opens to the inner circumferential side of the nut body 10 is provided at the other end of the first circulation path M. When viewed from the radially outer side, the first opening M3 is located between the second threads 5 and overlaps with the groove bottom 8. A second opening N3 that opens to the inner circumferential side of the nut body 10 is provided at the other end of the second circulation path N. When viewed from the radially outer side, the second opening N3 is located between the second threads 5 and closer to the second direction X2 than the first opening M3 and overlaps with the groove bottom 8. That is, the first opening M3 and the second opening N3 open toward the end 11a of the first thread 11.

[0028] According to the above-described circulating component 4, as shown in FIG. 5, the ball 3 that rolls on the first trackway L1 enters the first opening M3 of the circulating component 4 in the first direction X1. Then, the ball 3 passes through the first circulation path M and moves in the second direction X2 along the second return path 16. Further, the ball 3 passes through the second circulation path N of the circulating component 4 arranged in the second direction X2 and returns from the second opening N3 to the first trackway L1. On the other hand, the ball 3 that rolls on the second trackway L2 enters the second opening N3 of the circulating component 4 in the first direction X1. Then, it passes through the second circulation path N and moves in the second direction X2 along the first return path 15. Further, the ball 3 passes through the first circulation path M of the circulating component 4 arranged in the second direction X2 and returns from the first opening M3 to the second trackway L2.

[0029] Next, the details of the configuration of the main body portion 40 will be described. As shown in FIG. 6, as a configuration in the vicinity of the first opening M3 and the second opening N3, the main body portion 40 includes a main body central wall portion 43 that axially partitions the first opening M3 and the second opening N3, a main body first bottom wall portion 44 disposed radially inward of the first opening M3, a main body first side wall portion 45 disposed in the first direction X1 of the first opening M3, a main body second bottom wall portion 46 disposed radially inward of the second opening N3, and a main body second side wall portion 47 disposed in the second direction of the second opening N3.

[0030] The connecting portion 50 includes a central wall portion 51 that extends from the main body central wall portion 43 toward the end portion 11a of the first thread 11, a first side wall portion 52 that extends from the main body first side wall portion 45 toward the end portion 11a of the first thread 11, and a second side wall portion 53 that extends from the main body second side wall portion 47 toward the end portion 11a of the first thread 11. Since the central wall portion 51, the first side wall portion 52, and the second side wall portion 53 extend from the configuration in the vicinity of the first opening M3 and the second opening N3, it can be said that the central wall portion 51, the first side wall portion 52, and the second side wall portion 53 extend from the edges of the first opening M3 and the second opening N3 or are connected to the edges of the first opening M3 and the second opening N3.

[0031] Between the central wall portion 51 and the first side wall portion 52, there is a first connecting path M4 that connects the first trackway L1 and the first circulation path M. Between the central wall portion 51 and the second side wall portion 53, there is a second connecting path N4 that connects the second trackway L2 and the second circulation path N. The groove widths of the first connecting path M4 and the second connecting path N4 are the same as the groove widths H1, H2 (see FIG. 4) of the first circulation path M and the second circulation path N. Also, the first connecting path M4 and the second connecting path N4 are covered by the outer surface 21 of the nut 1, similar to the first circulation path M and the second circulation path N (see FIGS. 7 to 10).

[0032] The central wall portion 51, the first side wall portion 52, and the second side wall portion 53 extend from the main body portion 40 to the same extent. The central wall portion 51 extends in the spiral direction. The tip portion 51a of the central wall portion 51 is in contact with the end portion 11a of the first thread 11. The first side wall portion 52 and the second side wall portion 53 face the second thread 5 in the radial direction. Note that the radially inner surface of the first side wall portion 52 and the radially inner surface of the second side wall portion 53 are radially spaced apart from the second thread 5 (see FIGS. 8 to 10).

[0033] As shown in FIG. 7, the radially inner end 51b of the tip portion 51a of the central wall portion 51 is disposed radially inward of the first thread 11 and is close to the groove bottom 8 of the screw shaft 2. Therefore, the vicinity of the radially inner end 51b of the tip portion 51a of the central wall portion 51 faces the second thread 5 in the axial direction.

[0034] The radially inner surface 51c of the central wall portion 51 extends linearly toward the first opening M3. Therefore, the radially inner surface 51c of the central wall portion 51 is spaced apart from the groove bottom 8 of the screw shaft 2 as it approaches the main body portion 40. Hereinafter, in the extending direction of the central wall portion 51, the side of the end portion 11a of the first thread 11 is referred to as the tip side, and the side of the first opening M3 is referred to as the base end side.

[0035] As shown in FIG. 8, the central wall portion 51 has one side surface 54 facing the first direction X1 and the other side surface 55 facing the second direction X2. One side surface 54 forms the wall surface of the first connection path M4. The other side surface 55 forms the wall surface of the second connection path N4. A first scooping-up portion 61 bulging in the first direction X1 is provided on the tip side of one side surface 54. A second scooping-up portion 62 bulging in the second direction X2 is provided on the tip side of the other side surface 55.

[0036] Note that the first scooping-up portion 61 and the second scooping-up portion 62 are line-symmetric with respect to the central wall portion 51. Therefore, the first scooping-up portion 61 will be described as a representative example, and the description of the second scooping-up portion 62 will be omitted.

[0037] As shown in FIG. 8, the cross-sectional shape of the first scooping-up portion 61 has an opposing surface 63 facing the groove bottom 8, an inclined surface 64 facing the radially outer side, and a top portion 65 that most protrudes in the first direction X1. The top portion 65 on the tip side of the first scooping-up portion 61 is located radially inward of the center O of the ball 3 that rolls on the groove bottom 8 of the screw shaft 2. Therefore, the ball 3 that has entered the first connection path M4 rides on the upper surface (inclined surface 64) of the first scooping-up portion 61. Note that in FIG. 8 and below, the inclined surface 64 is linear, but it may be an arc surface extending along the ball 3 and is not particularly limited in the present disclosure.

[0038] Also, as shown in FIG. 8, the inclined surface 64 is inclined so as to be gradually located radially inward in the first direction X1. Therefore, the ball 3 that has ridden on the inclined surface 64 is displaced in the first direction X1. As a result, as shown in FIG. 9, the ball 3 abuts against the inner surface 52a of the first side wall portion 52. Therefore, the ball 3 that has entered the first connection path M4 moves through the first connection path M4 while abutting against (being supported by) the two surfaces of the inclined surface 64 and the inner surface 52a.

[0039] Also, as shown in FIG. 7, the first scooping-up portion 61 extends from the tip side (end portion of the first thread) of the central wall portion 51 to the base side (side of the first opening M3) of the central wall portion 51. And the base of the first scooping-up portion 61 is connected to the main body first bottom wall portion 44 inside the radial direction of the first opening M3. Therefore, the ball 3 that has entered the first connection path M4 moves while being supported by the two surfaces of the inclined surface 64 and the inner surface 52a, and enters the first opening M3.

[0040] Also, as shown in FIGS. 8, 9, and 10, the cross-sectional shape of the first scooping-up portion 61 has an increasing amount of bulging in the first direction X1 as it approaches the main body first bottom wall portion 44. To explain in detail, as shown in FIG. 8, the top portion 65 of the first scooping-up portion 61 is located in the second direction X2 from the center O of the ball 3. And it is located in the first direction X1 as it approaches the first opening M3. And as shown in FIG. 10, the top portion 65 of the first scooping-up portion 61 overlaps with the central portion in the groove width direction of the main body first bottom wall portion 44 in the radial direction. Therefore, the ball 3 that has entered the first connection path M4 surely moves in the first direction X1. That is, the ball 3 surely abuts against the inner surface 52a as well. Therefore, the ball 3 is surely supported by the two surfaces of the inclined surface 64 and the inner surface 52a, and the behavior of the ball 3 becomes stable. Accordingly, the entry of the ball 3 into the first opening M3 also becomes smooth.

[0041] As shown in FIG. 7, when viewed from the axial direction, the first scooping-up portion 61 extends in a substantially straight line. Also, the first scooping-up portion 61 extends in the tangential direction with respect to the groove bottom 8 of the screw shaft 2. For this reason, the scooping-up by the first scooping-up portion 61 (entry from the first rolling path L1 to the first connection path M4) becomes smooth. Also, the ball 3 moves linearly along the straight-line path of the first connection path M4. From the above, the movement from the first rolling path L1 to the first circulation path M1 via the first connection path M4 becomes smooth, and the operability of the ball screw device 100 is improved.

[0042] According to the ball screw device 100 of the embodiment described above, the ball 3 that has entered the first connection path M4 is carried to the first opening M3 while being supported by the two surfaces of the inclined surface 64 and the inner surface 52a. Similarly, the ball 3 that has entered the second connection path N4 is carried to the second opening N3 while being supported by two surfaces. That is, according to the embodiment, the ball 3 is not scooped up incorrectly. Therefore, the situation where the ball falls into the gap between the scooping-up part (the first scooping-up part 61 and the second scooping-up part 62) and the groove bottom 8 of the ball screw 2 does not occur. Accordingly, damage to the circulating component 4 is avoided.

[0043] As described above, the ball screw device 100 of the embodiment includes a nut 1 provided with a first thread 11 on its inner peripheral surface, a screw shaft 2 provided with a second thread 5 on its outer peripheral surface, a plurality of balls 3 arranged in an orbital path between the nut 1 and the screw shaft 2, and a circulation component 4 fixed to the nut 1 and provided with a first circulation path M and a second circulation path N. The first thread 11 and the second thread 5 are arranged so as to be displaced in the axial direction parallel to the axis X of the screw shaft 2. The nut 1 has a housing portion 20 formed by recessing its inner peripheral surface radially outward to house the circulation component 4. The first thread 11 has an end portion 11a formed by being cut out by the housing portion 20. The circulation component 4 is an entrance / exit of the first circulation path M and the second circulation path N, and includes a main body portion 40 provided with a first opening M3 and a second opening N3 that open toward the end portion 11a of the first thread 11, and a connection portion 50 that extends from the main body portion 40 toward the end portion 11a of the first thread 11 and scoops up the balls 3 in the tangential direction and guides them to the first opening M3 and the second opening N3. The connection portion 50 has a central wall portion 51 that extends from between the first opening M3 and the second opening N3 to the end portion 11a of the first thread 11, a first side wall portion 52 that is arranged on one side in the axial direction from the central wall portion 51 and extends while facing the second thread 5 in the radial direction, and a second side wall portion 53 that is arranged on the other side in the axial direction from the central wall portion 51 and extends while facing the second thread 5 in the radial direction. At a portion of the central wall portion 51 near the end portion 11a of the first thread 11, a first scooping-up portion 61 that bulges from one axial side surface 54 of the central wall portion 51, scoops up the ball 3 radially inside the center O of the ball 3, and scoops up the ball 3 from the other side in the axial direction from the center O of the ball 3, and a second scooping-up portion 62 that bulges from the other axial side surface 55 of the central wall portion 51, scoops up the ball 3 radially inside the center O of the ball 3, and scoops up the ball 3 from one side in the axial direction from the center O of the ball 3 are provided. The first scooping-up portion 61 extends along the central wall portion 51 to the first opening M3. The second scooping-up portion 62 extends along the central wall portion 51 to the second opening N3.

[0044] According to the ball screw device 100 of the embodiment, the ball 3 is not scooped up incorrectly. Therefore, it does not occur that the ball falls into the gap between the scooping-up part (the first scooping-up part 61 and the second scooping-up part 62) and the groove bottom 8 of the ball screw 2, and damage to the circulation component 4 is suppressed.

[0045] As described above, the ball screw device 100 of the embodiment has been described. However, the present disclosure is not limited to the examples described in the embodiment. For example, the inclined surface 64 may be arc-shaped along the rolling surface of the ball 3, and the cross-sectional shapes of the first scooping-up part 61 and the second scooping-up part 62 are not particularly limited. Further, in the embodiment, an example applied to the end deflector has been given. However, the present disclosure is not limited to this, and it may be applied to the shuttle type (deflector).

Description of Reference Numerals

[0046] 100 Ball screw device 1 Nut 2 Screw shaft 3 Ball 4 Circulation component 5 Second thread 6 One side surface 7 The other side surface 10 Nut body 11 First thread 12 One side surface 13 The other side surface 14 Groove bottom 20 Accommodating part 21 Outer side surface 22 Bottom surface 40 Body part 43 Body central wall part 44 Body first bottom wall part 45 Body first side wall part 46 Body second bottom wall part 47 Body second side wall part 50 Connection part 51 Central wall part 52 First side wall part 52a Inner surface 53 Second side wall part 54 One side surface 55 The other side surface 61 First scooping-up part 62 Second scooping-up part 63 Opposite surface 64 Inclined surface 65 Top part L1 First track L2 Second track M First circulation path M3 First opening N Second circulation path N3 Second opening

Claims

【Claim 1】 A nut having a first thread on its inner peripheral surface, A screw shaft having a second thread on its outer peripheral surface, A plurality of balls disposed in an orbital path between the nut and the screw shaft, A circulation component fixed to the nut and provided with a first circulation path and a second circulation path, comprising: The first thread and the second thread are arranged offset in an axial direction parallel to the axis of the screw shaft, The nut is formed by recessing the inner peripheral surface radially outward, and has a housing portion for housing the circulation component, The first thread has an end portion cut out by the housing portion, The circulation component A main body portion that is an entrance and exit of the first circulation path and the second circulation path, and is provided with a first opening and a second opening that open toward the end portion of the first thread, A connecting portion that extends from the main body portion toward the end portion of the first thread, scoops up the balls in a tangential direction, and guides them to the first opening and the second opening, having: The connecting portion A central wall portion that extends from between the first opening and the second opening toward the end portion of the first thread, A first side wall portion that is disposed on one side of the central wall portion in the axial direction and extends while facing the second thread in the radial direction, A second side wall portion that is disposed on the other side of the central wall portion in the axial direction and extends while facing the second thread in the radial direction, having: At a portion of the central wall portion closer to the end portion of the first thread, A first scooping-up portion that bulges out from one axial side surface of the central wall portion, scoops up the balls radially inside the center of the balls, and scoops up the balls from the other side in the axial direction than the center of the balls, A second scooping portion that bulges from the other axial side surface of the central wall portion, scoops up the ball from a position radially inside the center of the ball and from one of the axial directions with respect to the center of the ball; is provided, The first scooping portion extends along the central wall portion to the first opening, The second scooping portion extends along the central wall portion to the second opening Ball screw device.

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