Ball screw device

Abstract

A direction in which a leg part is inserted into a through hole is defined as an insertion direction, a direction opposite to the insertion direction is defined as a detachment direction, a direction parallel to an imaginary line connecting a pair of through holes when viewed from the detachment direction is defined as a longitudinal direction, and a direction orthogonal to the insertion direction and the longitudinal direction is defined as an orthogonal direction. A circulation component is composed of a first component and a second component. A dividing line for dividing the first component and the second component extends in the longitudinal direction when viewed from the orthogonal direction. The first component has a first body part and a pair of first leg parts. The second component has a second body part and a pair of second leg parts. A protruding part that protrudes outward in the longitudinal direction from the first leg parts is formed at an end portion of the first component in the return path direction. The protruding part abuts against the inner peripheral surface of the through hole from the inside in the longitudinal direction. An opening surrounded by the first leg parts and the protruding part is defined at an end portion of the first component. The end surface of the second component in the return path direction faces the surface of the protruding part in the detachment direction.

Description

Ball screw device

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

[0002] A ball screw device is a device that converts rotational motion into linear motion or converts linear motion into rotational motion. The ball screw device includes a screw shaft, a nut, a plurality of balls that roll along a track between the screw shaft and the nut, and a circulation component that returns the balls that have rolled from one end of the track to the other end to the one end of the track.

[0003] There are various types of circulation components, and one of them is the tubular circulation component shown in Patent Document 1 (hereinafter, may be simply referred to as a circulation component). The internal space of the circulation component serves as a return path. Also, openings are formed at both ends of the circulation component. A through-hole is formed in the nut that penetrates the outer peripheral surface and the inner peripheral surface of the nut. Both ends of the circulation component are inserted into the through-hole from the outer peripheral side of the nut. Then, the balls that roll along the track enter the return path from the opening of the circulation component. The balls move along the return path and circulate into the track from the other opening.

[0004] Japanese Patent No. 4525233

[0005] By the way, the circulation component of Patent Document 1 is composed of two components divided in the axial direction. Therefore, before assembling the circulation component to the nut, it is necessary to combine the two components, and improvement in the assemblability of the circulation component is required.

[0006] The present disclosure has been made in view of the above, and an object thereof is to provide a ball screw device with improved assemblability of a circulation component.

[0007] To achieve the above objective, a ball screw device according to one aspect of the present disclosure comprises a screw shaft, a nut into which the screw shaft is inserted, a plurality of balls arranged in a raceway between the screw shaft and the nut, and a tubular circulating component having a return path formed inside and openings formed on both end faces. The nut has a pair of through holes that penetrate the outer and inner circumferential surfaces of the nut. The circulating component has a pair of legs inserted into the pair of through holes, and a main body connecting the pair of legs. The insertion direction is parallel to the through holes and the direction in which the legs are inserted into the through holes. The disengagement direction is the direction opposite to the insertion direction. The longitudinal direction is the direction parallel to the imaginary line connecting the pair of through holes when viewed from the disengagement direction. The orthogonal direction is the direction perpendicular to the insertion direction and the longitudinal direction, respectively. The circulating component is composed of a divisible first component and a second component. The dividing line separating the first component and the second component extends in the longitudinal direction when viewed from the orthogonal direction. The first component comprises a first main body portion that constitutes a part of the main body portion, and a pair of first legs portion that constitute a part of the leg portion. The second component comprises a second main body portion that constitutes the remainder of the main body portion and is positioned relative to the first main body portion in the detachment direction, and a pair of second legs portion that constitute the remainder of the leg portion and is positioned outward in the longitudinal direction relative to the first leg portion. The direction in which the return path extends is defined as the return path direction. A projection is formed at the end of the first component in the return path direction, projecting outward from the first leg portion in the longitudinal direction. The projection extends along the inner circumferential surface of the through hole and abuts against the inner circumferential surface of the through hole from the inside in the longitudinal direction. An opening is formed at the end of the first component in the return path direction, surrounded by the first leg portion and the projection. The end face of the second component in the return path direction faces the detachment direction face of the projection.

[0008] The second component of this disclosure is positioned on the outside of the first component in both the detachment direction and the longitudinal direction. In other words, the second component is positioned in the detachment direction of the first component. This allows the first component and then the second component to be assembled to the nut in that order. Thus, this disclosure eliminates the need to combine the first and second components before assembling them to the nut, improving ease of assembly. Furthermore, the protrusions at both ends of the first component abut against the inner circumferential surface of the through hole from the inside in the longitudinal direction. Therefore, longitudinal misalignment (looseness) of the first component is restricted.

[0009] Furthermore, in the aforementioned ball screw device, the pair of protrusions press the inner circumferential surfaces of the pair of through holes outward in the longitudinal direction due to elastic deformation.

[0010] According to the above configuration, the first component is assembled to the nut while being braced in the longitudinal direction. This further restricts the longitudinal displacement (looseness) of the first component.

[0011] Furthermore, the ball screw device described above has a sleeve that fits onto the outer circumference of the nut. The second component is in contact with the inner surface of the sleeve.

[0012] According to the above configuration, the circulating component will not fall off the nut.

[0013] Furthermore, in the ball screw device described above, the sleeve presses the second component in the insertion direction. The second component presses the first component in the insertion direction. The first component is pressed against the outer circumference of the nut.

[0014] According to the above configuration, the first component is held between the second component and the nut. Therefore, misalignment (looseness) of the first component is restricted.

[0015] Furthermore, in the ball screw device described above, a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut. The second component is press-fitted into the housing portion.

[0016] According to the above configuration, the circulating component will not fall off the nut.

[0017] Furthermore, in the ball screw device described above, a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut. The second component may be fitted into the housing portion through a gap fit.

[0018] Furthermore, in the ball screw device described above, a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut. The second component has at least one protrusion that projects toward the inner surface of the housing portion. The protrusion is flattened between the second component and the inner surface of the housing portion.

[0019] According to the above configuration, the movement of the second component in the detachment direction is restricted, and the circulating component does not fall off the nut.

[0020] Furthermore, in the ball screw device described above, one end of the protrusion is connected to the first leg. The other end of the protrusion does not need to be connected to the first leg.

[0021] Furthermore, in the ball screw device described above, both ends of the protruding portion may be connected to the first leg portion.

[0022] Furthermore, in the ball screw device described above, the projection may have two longitudinal projections that extend linearly in the longitudinal direction and are spaced apart from each other in the orthogonal direction, and an orthogonal projection that extends linearly in the orthogonal direction and connects to the outer ends of the two longitudinal projections in the longitudinal direction.

[0023] Furthermore, in the ball screw device described above, the projection has two partial projections that are divided into two in the orthogonal direction. The inner end of the partial projection in the longitudinal direction may be connected to the first leg.

[0024] Furthermore, in the ball screw device described above, a fitting groove is formed on the inner circumferential surface of the through hole into which the protruding portion fits.

[0025] According to the above configuration, the protruding portion catches in the groove, restricting displacement (looseness) in the insertion or removal direction.

[0026] Furthermore, in the ball screw device described above, the first component has a first opposing surface that faces the second component. The first opposing surface may have a groove surface formed thereon, with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction.

[0027] Furthermore, in the ball screw device described above, the second component has a second opposing surface that faces the first component. The second opposing surface may have a groove surface formed thereon, with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction.

[0028] Furthermore, in the ball screw device described above, the first component has a first opposing surface facing the second component. The second component has a second opposing surface facing the first component. The first opposing surface has a surface formed thereon with a straight cross-sectional shape when cut in a direction perpendicular to the return path direction. The second opposing surface may have a grooved surface formed thereon with a U-shaped cross-sectional shape when cut in a direction perpendicular to the return path direction.

[0029] Furthermore, in the ball screw device described above, the first component may be made of metal and manufactured by deep drawing, punching, pressing, or metal powder injection molding.

[0030] Furthermore, in the ball screw device described above, the first component may be made of resin and manufactured by resin injection molding.

[0031] Furthermore, in the ball screw device described above, the second component may be made of metal and manufactured by deep drawing, punching, pressing, or metal powder injection molding.

[0032] Furthermore, in the ball screw device described above, the second component may be made of resin and manufactured by resin injection molding.

[0033] The ball screw device of this disclosure improves the ease of assembly of circulating parts.

[0034] Figure 1 is a cross-sectional view of the ball screw device of Embodiment 1, cut along the central axis. Figure 2 is an exploded perspective view of the ball screw device of Embodiment 1. Figure 3 is a view of the nut housing of Embodiment 1 from the detachment direction. Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 3. Figure 5 is a view of the circulating component of Embodiment 1 (before assembly to the nut) from the orthogonal direction. Figure 6 is a cross-sectional view of the ball screw device of Embodiment 1 (a cross-sectional view taken along the line VI-VI in Figure 3). Figure 7 is a cross-sectional view of the main body of the circulating component of Embodiment 1, cut in a direction perpendicular to the longitudinal direction. Figure 8 is an exploded perspective view of the circulating component of Embodiment 1. Figure 9 is a view of the first component assembled to the housing in Embodiment 1 from the detachment direction. Figure 10 is a view of the first component of Modification 1 from the detachment direction. Figure 11 is a view of the first component of Modification 2 from the detachment direction. Figure 12 is a view of the first component of Modification 3 from the detachment direction. Figure 13 is a cross-sectional view of the housing section of Modification 4, cut in the longitudinal direction. Figure 14 is a perspective view of the second part of Modification 5. Figure 15 is a cross-sectional view of the circulating part of Modification 6, cut in a direction perpendicular to the longitudinal direction. Figure 16 is a cross-sectional view of the circulating part of Modification 7, cut in a direction perpendicular to the longitudinal direction.

[0035] The embodiments for carrying out the invention will be described in detail with reference to the drawings. This disclosure is not limited by the contents described below. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate.

[0036] (Embodiment 1) Figure 1 is a cross-sectional view of the ball screw device of Embodiment 1, cut along the central axis. Figure 2 is an exploded perspective view of the ball screw device of Embodiment 1. As shown in Figures 1 and 2, the ball screw device 100 of Embodiment 1 comprises a screw shaft 1, a nut 2, a plurality of balls 3, two circulating parts 4, and a sleeve 5.

[0037] A helical outer raceway surface 10 is formed on the outer surface of the screw shaft 1. In the following description, the direction parallel to the central axis O1 of the screw shaft 1 is referred to as the axial direction. The direction perpendicular to the central axis O1 is referred to as the radial direction. Within the radial direction, the direction toward the central axis O1 is referred to as the radially inward direction, and the direction opposite to the radially inward direction is referred to as the radially outward direction.

[0038] The nut 2 is formed in a cylindrical shape with a central axis O1. As shown in Figure 1, a helical inner raceway surface 22 is formed on the inner circumferential surface 20 of the nut 2. The inner raceway surface 22 faces the outer raceway surface 10. The space between the inner raceway surface 22 and the outer raceway surface 10 constitutes a raceway. Multiple balls 3 are arranged in the raceway. In this embodiment, the length of the raceway is approximately 2.5 turns. However, the length of the raceway may be other than 2.5 turns, and is not particularly limited in this disclosure.

[0039] Two housing portions 30 for accommodating the circulating component 4 are formed on the outer circumferential surface 21 of the nut 2. In this embodiment, there are two circulating components 4 and two housing portions 30, but this disclosure does not limit the number to one or three or more. In addition, an annular groove 23 is formed on one end of the outer circumferential surface 21 of the nut 2 in the axial direction.

[0040] As shown in Figure 2, the circulating component 4 is composed of a first component 50 and a second component 60. The method of assembling the circulating component 4 to the nut 2 is to insert the circulating component 4 into the housing 30 from the radially outer side of the housing 30 (see arrow A1 in Figure 2). Hereinafter, the direction parallel to arrow A1 and pointed to by arrow A1 will be referred to as the insertion direction X1.

[0041] The sleeve 5 is a cylindrical component. The method of attaching the sleeve 5 to the nut 2 is as shown in Figure 2, by moving the sleeve 5 axially (see arrow A2 in Figure 2) and inserting the nut 2 into the inside of the sleeve 5. As shown in Figure 1, the sleeve 5 covers the outer circumferential surface 21 of the nut 2 and the circulating component 4. This restricts the movement of the circulating component 4 in the direction opposite to the insertion direction X1, preventing it from falling out of the housing 30. Hereinafter, the direction opposite to the insertion direction X1 will be referred to as the release direction X2.

[0042] As shown in Fig. 1, at one axial end of the sleeve 5, a clamping portion 5a is formed by clamping a part of the sleeve 5 radially inward. The clamping portion 5a is engaged with the groove 23. Therefore, the sleeve 5 is restricted from moving axially and does not fall off from the nut 2. Note that the sleeve in Fig. 2 shows the state before clamping (before attaching to the nut 2), and the clamping portion 5a is not formed. Also, although the sleeve 5 of the present embodiment is cylindrical, the present disclosure may be C-shaped when viewed from the axial direction, and there is no particular limitation. Also, the method of fixing the sleeve 5 to the nut 2 may be a fixing method other than clamping, and there is no particular limitation on the fixing method.

[0043] Next, the details of the accommodating portion 30 and the circulation component 4 will be described.

[0044] Fig. 3 is a view of the nut accommodating portion of Embodiment 1 as viewed from the detachment direction. Fig. 4 is a cross-sectional view taken along the line IV-IV in Fig. 3. As shown in Figs. 3 and 4, the accommodating portion 30 includes a pair of through holes 31 and a recess 32 provided between the pair of through holes 31.

[0045] Note that the center line K31 shown in Fig. 4 is the center line of the through hole 31. As shown in Fig. 4, the through hole 31 penetrates the inner peripheral surface 20 and the outer peripheral surface 21 of the nut 2. The direction in which the through hole 31 extends (center line K31) is parallel to the insertion direction X1 (or the detachment direction X2).

[0046] As shown in Fig. 3, when viewed from the detachment direction X2, the through hole 31 is formed in a circular shape centered on the center line K31. Therefore, the inner peripheral surface 33 of the through hole 31 is also formed in a circular shape centered on the center line K31. Also, on the inner peripheral surface 33 of the through hole 31, a C-shaped seating surface 34 that protrudes into the through hole 31 is formed.

[0047] As shown in Fig. 4, the seating surface 34 is disposed at the end of the inner peripheral surface 33 of the through hole 31 in the insertion direction X1. Also, the seating surface 34 faces the detachment direction X2. Note that the seating surface 34 of the present embodiment overlaps with the inner peripheral track surface 22 and is partially cut out as shown in Fig. 4. Therefore, the seating surface 34 of the present embodiment is C-shaped when viewed from the detachment direction X, but the present disclosure may have a seating surface other than C-shaped, and there is no particular limitation.

[0048] Next, the recess 32 will be described. As shown in FIG. 3, a virtual straight line connecting the center lines K31 of the pair of through holes 31 is defined as a virtual line K30. A direction parallel to the virtual line K30 is referred to as a longitudinal direction Y. Further, in the longitudinal direction Y, a direction in which an intermediate point C of the virtual line K30 is arranged when viewed from the through hole 31 is referred to as the inner side of the longitudinal direction Y, and the opposite direction is referred to as the outer side of the longitudinal direction Y. Also, a direction orthogonal to each of the insertion direction X1 (or the removal direction X2) and the longitudinal direction Y is referred to as an orthogonal direction Z.

[0049] As shown in FIG. 4, the recess 32 is a depression formed in the outer peripheral surface 21 of the nut 2. Therefore, unlike the through hole 31, the recess 32 has a bottom surface 35. Further, the direction in which the recess 32 departs from the outer peripheral surface 21 of the nut 2 (the direction in which the recess 32 extends) is parallel to the insertion direction X1 (or the removal direction X2). Also, when viewed from the removal direction X2, as shown in FIG. 3, the recess 32 is linearly formed so as to overlap the virtual line K30.

[0050] As shown in FIG. 4, the central portion in the longitudinal direction Y of the bottom surface 35 of the recess 32 is a plane 36 orthogonal to the insertion direction Z1. Also, both end portions in the longitudinal direction Y of the bottom surface 35 are arcuate curved surfaces 37. The curved surface 37 is inclined so as to be positioned in the insertion direction X1 as it goes toward the outer side of the longitudinal direction Y. Also, the end portion in the longitudinal direction Y of the curved surface 37 is connected to the end portion of the seating surface 34 (see FIG. 3).

[0051] As shown in FIG. 3, the recess 32 has a pair of first side surfaces 38 facing each other in the orthogonal direction Z. The distance between the pair of first side surfaces 38 (the size of the accommodating portion 30 in the orthogonal direction Z) is L1. Also, the distance between the inner peripheral surfaces 33 of the pair of through holes 31 (the size of the accommodating portion 30 in the longitudinal direction Y) is L2.

[0052] Figure 5 is a view of the circulation component of Embodiment 1 (before assembly to the nut) from a perpendicular direction. As shown in Figure 5, the circulation component 4 is a tubular component. The internal space of the circulation component 4 constitutes a return path 40 through which the ball 3 passes. The circulation component 4 is also formed in a U-shape (C-shape) when viewed from the perpendicular direction Z. The end face 43 of the circulation component 4 faces the insertion direction X1. An opening 44 is formed on the end face 43 of the circulation component 4. Furthermore, a tongue 45 for scooping up the ball 3 is formed on the end face 43 of the circulation component 4.

[0053] Figure 6 is a cross-sectional view of the ball screw device of Embodiment 1 (a cross-sectional view taken along the line VI-VI in Figure 3). When the circulating component 4 is inserted into the housing section 30, the circulating component 4 is divided into a portion that is placed in the through hole 31 and a portion that is placed in the recess 32. Hereinafter, the portion of the circulating component 4 that is placed in the through hole 31 will be referred to as the leg portion 41, and the portion that is placed in the recess 32 will be referred to as the main body portion 42.

[0054] Figure 7 is a cross-sectional view of the main body of the circulation component of Embodiment 1, cut in a direction perpendicular to the longitudinal direction. As shown in Figure 7, the cross-sectional shape of the return path 40 (the inner circumferential surface 46 of the return path 40) cut in a direction perpendicular to the center line O40 of the return path 40 is circular.

[0055] As shown in Figure 5, the return path 40 formed in the main body 42 extends in the longitudinal direction Y at the center of the main body 42. The return path 40 gradually curves so as it moves outward in the longitudinal direction Y, it is positioned in the insertion direction X1. The return path 40 formed in the leg portion 41 extends in the insertion direction X1 (or the disengagement direction X2). The openings 44 located at both ends of the return path 40 open in the insertion direction X1. From the above, when viewed from the orthogonal direction Z, the return path 40 is formed in a U-shape (C-shape). Hereinafter, the direction in which the return path 40 extends will be referred to as the return path direction.

[0056] Furthermore, when the circulating component 4 is assembled into the housing section 30, as shown in Figure 6, the tongue 45 of the circulating component 4 is positioned on the inner circumference side of the nut 2. In addition, the opening 44 opens toward the inner circumference side of the nut 2. As a result, the ball 3 that has moved to one end of the track is picked up by the tongue 45 and enters the opening 44. The ball 3 that has entered the opening 44 then moves along the return path 40 and exits through the other opening 44, circulating to the other end of the track.

[0057] As shown in Figure 5, the circulation component 4 is composed of a first component 50 and a second component 60. The dividing line 70 that separates the first component 50 and the second component 60 extends in the longitudinal direction when viewed from the orthogonal direction Z. Furthermore, the dividing line 70 that separates the first component 50 and the second component 60 overlaps with the portion of the return path 40 excluding the opening 44 when viewed from the orthogonal direction Z. In addition, the dividing line 70 in this embodiment overlaps with the center line O40 of the return path 40 when viewed from the orthogonal direction Z. Moreover, the first component 50 is made of metal and is formed by deep drawing. The second component 60 is made of resin and is formed by resin injection molding.

[0058] Figure 8 is an exploded perspective view of the circulating component of Embodiment 1. The first component 50 has a pair of first legs 51 and a first body 52 connecting the pair of first legs 51. The second component 60 has a pair of second legs 61 and a second body 62 connecting the pair of second legs 61.

[0059] As shown in Figure 5, the first leg portion 51 is part of the leg portion 41 and is positioned inward in the longitudinal direction Y from the center line O40 of the leg portion 41. The first main body portion 52 is part of the main body portion 42 and is positioned in the insertion direction X1 from the center line O40 of the main body portion 42.

[0060] The outer surface of the first leg portion 51 in the longitudinal direction Y and the surface of the first main body portion 52 in the detachment direction X2 form the first opposing surface 71 that faces the second part 60. As shown in Figure 8, a first groove surface 46a is formed on the first opposing surface 71. The cross-sectional shape of the first groove surface 46a, when cut in a direction perpendicular to the return path direction, is arc-shaped (semicircular). As shown in Figure 7, the first groove surface 46a constitutes a part of the inner circumferential surface 46 surrounding the return path 40.

[0061] As shown in Figure 5, the second leg portion 61 is part of the leg portion 41 and is located outside the longitudinal direction Y of the leg portion 41 relative to the center line O40. The second main body portion 62 is part of the main body portion 42 and is located in the direction away from the center line O40 X2 of the main body portion 42.

[0062] The inner surface of the second leg portion 61 in the longitudinal direction Y and the surface of the second main body portion 62 in the insertion direction X1 form a second opposing surface 72 that faces the first component 50. As shown in Figure 7, a second groove surface 46b is formed on this second opposing surface 72, with a cross-sectional shape that is arc-shaped (semicircular) when cut in a direction perpendicular to the return path direction. This second groove surface 46b is the remainder of the inner circumferential surface 46 surrounding the return path 40 (see Figure 7).

[0063] As shown in Figure 5, a tongue 45 is formed at the end 51a of the first leg portion 51 in the return direction, projecting in the insertion direction X1. In addition, a projection 55 is formed at the end 51a of the first leg portion 51 in the return direction (insertion direction X1), projecting outward from the first leg portion 51 in the longitudinal direction Y.

[0064] As shown in Figure 8, the protrusion 55 is formed in a C-shape when viewed from the detachment direction X2. One end of the protrusion 55 is connected to the end 51a of the first leg portion 51. On the other hand, the other end of the protrusion 55 is not connected to the end 51a of the first leg portion 51. The surface 55a of the protrusion 55 in the detachment direction X2 faces the end face 60a of the second part 60 in the return direction. In other words, the protrusion 55 is positioned in the insertion direction X1 relative to the end face 60a of the second part 60 in the return direction.

[0065] Figure 9 is a view of the first component assembled in the housing in Embodiment 1, as seen from the detachment direction. As shown in Figure 9, the protruding portion 55, when assembled in the housing 30, extends along the inner circumferential surface 33 of the through hole 31. Therefore, an opening 44 is formed at the end of the first component 50 in the return path direction, surrounded by the first groove surface 46a formed on the end 51a of the first leg portion 51 and the protruding portion 55. From the above, it can be seen that the opening 44 is formed in the first component 50 but not in the second component 60.

[0066] As described above, as shown in Figure 5, the first part 50 and the second part 60 are formed in a U-shape (C-shape) when viewed from the orthogonal direction Z. The second part 60 is positioned on the outer circumference of the U-shape (C-shape) formed by the first part 50. Furthermore, the protruding portion 55 of the first part 50 is positioned in the insertion direction X1 relative to the second part 60. Therefore, the first part 50 and the second part 60 can be separated in the insertion direction X1 (or the removal direction X2). For this reason, the assembly of the circulating part 4 to the nut 2 can be performed by first assembling the first part 50 into the housing part 30, and then assembling the second part 60 into the housing part 30.

[0067] Next, the other configurations of the first part 50 and the second part 60 will be described. Before assembly to the housing section 30, the magnitude of the first part 50 in the orthogonal direction Z is the same as the magnitude L1 of the housing section 30 in the orthogonal direction Z (see Figure 3). Therefore, as shown in Figure 7, the first part 50 is in contact with each of the pair of first side surfaces 38. For this reason, the misalignment (play) of the first part 50 in the orthogonal direction Z is restricted.

[0068] As shown in Figure 6, the first main body portion 52 of the first component 50 is in contact with the flat surface 36 of the bottom surface 35 of the housing portion 30. Therefore, the first component 50 is restricted from misalignment (looseness) in the insertion direction X1. Note that the first component 50 is not in contact with the curved surface 37 of the bottom surface 35.

[0069] The first opposing surface 71 of the first part 50 is in contact with the second opposing surface 72 of the second part 60. Therefore, the first part 50 is restricted from misalignment (looseness) in the detachment direction X2.

[0070] As shown in Figure 9, the protruding portion 55 is in contact with the inner circumferential surface 33 of the through hole 31. Therefore, the first component 50 is restricted from misalignment (looseness) in the longitudinal direction Y.

[0071] As shown in Figure 5, the length Y of the first part 50 before assembly to the housing 30 is larger than the length Y of the housing 30, L2 (see Figure 3). Therefore, when assembling the first part 50 to the housing 30, the protruding part 55 is pressed from the outside in the length Y (see arrow B1 in Figure 5). In other words, the protruding part 55 is assembled to the housing 30 in a state where it is deformed inward in the length Y (the C-shape is reduced in diameter).

[0072] Therefore, after assembly to the housing section 30, the protruding portion 55 presses the inner circumferential surface 33 of the through hole 31 outward in the longitudinal direction Y due to elastic deformation (see arrow B2 in Figure 9). In other words, the first component 50 is assembled to the housing section 30 while being braced in the longitudinal direction Y. As a result, displacement (looseness) of the first component 50 in the longitudinal direction Y is restricted.

[0073] As shown in Figure 6, the protruding portion 55 is sandwiched between the seat surface 34 and the second component 60. This restricts the first leg portion 51 from shifting (loosening) in the insertion direction X1 and the removal direction. As a result, the tongue 45 provided on the first leg portion 51 is positioned in a predetermined location, and the ball 3 is scooped up smoothly.

[0074] As shown in Figures 5 and 8, the second part 60 has a pair of first sides 65 facing the orthogonal direction Z, a pair of second sides 66 facing the longitudinal direction Y, and an outer side 67 facing the detachment direction X2.

[0075] Before assembly into the housing section 30, the size of the second part 60 in the orthogonal direction Z (distance between the pair of first side surfaces 65) is slightly larger than the size L1 of the housing section 30 in the orthogonal direction Z (see Figure 3). Also, as shown in Figure 5, before assembly into the housing section 30, the size L22 of the second part 60 in the longitudinal direction Y (distance between the pair of second side surfaces 66) is larger than the size L2 of the housing section 30 in the longitudinal direction Y (see Figure 3). In other words, the second part 60 has overlapping allowance in the orthogonal direction Z and the longitudinal direction Y relative to the housing section 30. Therefore, the second part 60 is inserted into the housing section 30 by press-fitting. For this reason, the second part 60 (circulating part 4) is difficult to move in the detachment direction X2.

[0076] Although not specifically shown in the diagram, when the first part 50 and the second part 60 are inserted sequentially into the housing part 30, the outer surface 67 of the second part 60 protrudes slightly in the disengagement direction X2 from the outer surface 21 of the nut 2. When the sleeve 5 is attached to the nut 2, the second part 60 is pressed in the insertion direction X1 by the sleeve 5. The second part 60 also presses the first part 50 in the insertion direction X1. Therefore, the first part 50 is held between the second part 60 and the bottom surface 35 (flat surface 36) of the housing part 30. This restricts the displacement (looseness) of the first part 50.

[0077] According to the embodiment 1 described above, the first part 50 and the second part 60 can each be assembled onto the nut 2. Therefore, the effort (work) of assembling the circulating part 4 by combining the first part 50 and the second part 60 can be eliminated. In other words, the ease of assembly of the circulating part 4 is improved.

[0078] Although Embodiment 1 has been described above, this disclosure is not limited to the example described in Embodiment 1. For example, in this disclosure, the size L12 (see Figure 5) of the longitudinal direction Y of the first part 50 and the size L2 of the longitudinal direction Y of the housing part 30 may be the same. Even with this first part 50, the protruding part 55 abuts against the inner circumferential surface 33 of the through hole 31, and the displacement (looseness) of the first part 50 in the longitudinal direction Y is restricted.

[0079] Furthermore, although the protrusion 55 in Embodiment 1 is formed in a C-shape (arc shape) when viewed from the detachment direction X2, other shapes are also possible in this disclosure. Below, Modifications 1 to 3 in which the shape of the protrusion 55 is changed will be described. In addition, the examples of Modifications 1 to 3 in which the protrusion does not press the inner circumferential surface 33 of the through hole 31 outward in the longitudinal direction Y due to elastic deformation will be described.

[0080] (Modifications 1 to 3) Figure 10 is a view of the first part of Modification 1 from the detachment direction. As shown in Figure 10, the protruding portion 55A of the first part 50A of Modification 1 is common with Embodiment 1 in that it is formed in a semicircular shape with respect to the center line K31. However, it differs from Embodiment 1 in that both ends of the protruding portion 55A are connected to the first leg portion 51. According to this Modification 1, the first groove surface 46a formed on the end 51a of the first leg portion 51 and the protruding portion 55A are formed in an annular shape and surround the entire outside of the opening 44.

[0081] Figure 11 is a view of the first part of Modified Example 2 from the detachment direction. As shown in Figure 11, the protruding portion 55B of the first part 50B of Modified Example 2 has two longitudinal protruding portions 155 that extend linearly in the longitudinal direction Y, and one orthogonal protruding portion 156 that extends linearly in the orthogonal direction Z. The longitudinal protruding portions 155 extend outward in the longitudinal direction Y from the end 51a of the first leg portion 51. The two longitudinal protruding portions 155 are spaced apart from each other in the orthogonal direction Z. Both ends of the orthogonal protruding portion 156 are connected to the outer ends of the two longitudinal protruding portions 155 in the longitudinal direction Y. The longitudinal protruding portions 155 and the orthogonal protruding portion 156 intersect at a right angle. In other words, the protruding portion 55B of Modified Example 2 is concave when viewed from the detachment direction X2. In the modified example 2, the inner circumferential surface 33 of the through hole 31 needs to be formed in a concave shape corresponding to the shape of the protrusion 55B. The present disclosure also includes a longitudinal protrusion 155 that is slightly inclined with respect to the longitudinal direction Y. Similarly, it includes a perpendicular protrusion 156 that is slightly inclined with respect to the perpendicular direction.

[0082] Figure 12 is a view of the first part of Modified Example 3 from the detachment direction. As shown in Figure 12, the projection 55C of the first part 50C of Modified Example 3 has two partial projections 255 which are divided into two parts in the orthogonal direction Z. The inner end of the partial projection 255 in the longitudinal direction Y is connected to the end 51a of the first leg 51. The two partial projections 255 are each formed in an arc shape and move closer to each other as they move outward in the longitudinal direction Y from the end 51a of the first leg 51. However, the outer ends of the two partial projections 255 in the longitudinal direction Y are not connected.

[0083] Although Modifications 1 to 3 have been described above, even with these modifications, the positional displacement (looseness) of the first part 50 in the longitudinal direction Y can be restricted in the same way as in Embodiment 1. Furthermore, this disclosure may also be made so that the protrusions 55A, 55B, and 55C shown in Modifications 1 to 3 exert elastic deformation force. Next, other modifications will be described.

[0084] (Modification 4) Figure 13 is a cross-sectional view of the housing portion of Modification 4, cut in the longitudinal direction. Modification 4 differs from Embodiment 1 in that a seating surface 34 (see Figure 3, etc.) is not formed in the through hole 31D. As shown in Figure 13, Modification 4 differs from Embodiment 1 in that a fitting groove 133 into which the protruding portion 55 fits is formed on the inner circumferential surface 33D of the through hole 31D. With this, the protruding portion 55 catches in the fitting groove 133, and positional displacement (looseness) in the insertion direction X1 and the removal direction X2 is restricted.

[0085] In modification 4, there is no seating surface 34, but the present disclosure may also include a seating surface 34 in addition to the fitting groove 133. This further restricts the positional displacement (looseness) of the protrusion 55 in the insertion direction X1.

[0086] (Modification 5) Figure 14 is a perspective view of the second part of Modification 5. As shown in Figure 14, the second part 60E of Modification 5 differs from Embodiment 1 in that it does not have an overlap with respect to the housing part 30. The second part 60E also differs from Embodiment 1 in that a plurality of protrusions 69 are formed on a pair of first side surfaces 65. These protrusions 69 are formed in a hemispherical shape. When the second part 60E is assembled to the housing part 30, the protrusions 69 are compressed and crushed between the first side surface 38 of the housing part 30 and the second part 60E. For this reason, the second part 60E is difficult to move in the detachment direction X2. In this embodiment, although the protrusions 69 are deformed (crushed), the second leg portion 61 and the second main body portion 62 are not deformed. That is, the first groove surface 46a formed on the second leg portion 61 and the second main body portion 62 is not deformed. Therefore, the ball 3 moves smoothly along the return path 40.

[0087] In Modification 5, multiple protrusions 69 are formed, but in this disclosure, at least one is sufficient. Also, in Modification 5, the protrusions 69 are formed on the first side surface 65, but in this disclosure, the protrusions 69 may be formed on the second side surface 66. Furthermore, although the protrusions 69 are crushed between the first side surface 38 and the second part 60E, this deformation may be elastic deformation or plastic deformation.

[0088] (Modification 6) Figure 15 is a cross-sectional view of the circulation component of Modification 6, cut in a direction perpendicular to the longitudinal direction. As shown in Figure 15, Modification 6 differs from Embodiment 1 in that the first opposing surface 71F of the first component 50F of the circulation component 4F does not have a first groove surface 46a (see Figure 7). In other words, the first opposing surface 71F of Modification 6 has a straight cross-sectional shape when cut in a direction perpendicular to the return path direction. Also, Modification 6 differs from Embodiment 1 in that the second groove surface 46b of the second component 60F has a U-shaped cross-sectional shape when cut in a direction perpendicular to the return path direction. In other words, the second opposing surface 72F of the second component 60F is positioned closer to the insertion direction X1 or further inward in the longitudinal direction Y than the second opposing surface 72 of Embodiment 1. From the above, when the dividing line 70F is viewed from the orthogonal direction Z, the dividing line 70F coincides with the return path 40 (excluding the opening 44) on the side closest to the insertion direction X1 or further inward in the longitudinal direction Y. This disclosure may be modified in the following ways.

[0089] (Modification 7) Figure 16 is a cross-sectional view of the circulating part of Modification 7, cut in a direction perpendicular to the longitudinal direction. As shown in Figure 16, the circulating part 4G of Modification 7 differs from Embodiment 1 in that a notch 77 is provided in the second part 60G that cuts out a part of the second opposing surface 72. The notch 77 cuts out a portion of the second opposing surface 72 that is located in the detachment direction X2 with respect to the plane 36 of the bottom surface 35 of the recess 32 (see Figures 4 and 6). The present disclosure may also be such a circulating part 4G.

[0090] Regarding the shape of the notch 77, this disclosure may provide a shape other than the notch 77 shown in Modified Example 7. Also, regarding the position of the notch 77, for example, the notch 77 may be provided so as to cut out a portion of the second opposing surface 72 that is located in the detachment direction X2 with respect to the curved surface 37 of the bottom surface 35 of the recess 32 (see Figures 4 and 6), and is not limited to the position shown in Modified Example 7.

[0091] The various modifications have been described above. In addition, in this embodiment, a sleeve 5 is used as a fixing part to prevent the circulating part 4 from falling out, but other fixing parts may be used. Also, if the second part 60 is fixed to the housing part 30 by press-fitting, it is not necessary to use fixing parts such as the sleeve 5.

[0092] Furthermore, in this disclosure, if the movement of the second component 60 in the detachment direction X2 is restricted by a fixing component such as the sleeve 5, the second component 60 may be loosely fitted into the housing 30. Also, in Embodiment 1, the second component 60 is provided with a tightening allowance in the longitudinal direction Y and a tightening allowance in the orthogonal direction Z, but in this disclosure, a tightening allowance may be provided in only one of the longitudinal direction Y and the orthogonal direction Z.

[0093] Furthermore, although the housing portion 30 of Embodiment 1 has a recess 32 in addition to the pair of through holes 31, the present disclosure does not require the recess 32. In other words, the main body portion 42 of the circulating component 4 may be positioned outside the outer peripheral surface 21 of the nut 2. Also, although the main body portion 42 (recess 32) is straight along the imaginary line K30 when viewed from the detachment direction X2, it may have other shapes such as curves.

[0094] Furthermore, in Embodiment 1, the protrusion 55 is sandwiched between the seat surface 34 and the second part 60, but in this disclosure, the protrusion 55 may only be in contact with either the seat surface 34 or the second part 60. Alternatively, in this disclosure, the protrusion 55 may not be in contact with either the seat surface 34 or the second part 60.

[0095] Furthermore, in Embodiment 1, the first metal part 50 is formed by deep drawing, but in this disclosure, it may be manufactured by punching, pressing, or metal powder injection molding. Also, in Embodiment 1, the second part 60 is made of resin, but in this disclosure, the second part may be made of metal. If the second part is made of metal, it may be manufactured by deep drawing, punching, pressing, or metal powder injection molding. Furthermore, in this disclosure, the first part may be a resin product manufactured by resin injection molding.

[0096] Furthermore, this disclosure may also be a combination of the following configurations. (1) A screw shaft, a nut into which the screw shaft is inserted, a plurality of balls arranged in a track between the screw shaft and the nut, and a tubular circulating part having a return path formed inside and openings formed on both end faces, wherein the nut has a pair of through holes that penetrate the outer and inner surfaces of the nut, the circulating part has a pair of legs inserted into the pair of through holes, and a main body that connects the pair of legs, the insertion direction is parallel to the through holes, the direction in which the legs are inserted into the through holes is defined as the release direction, the direction opposite to the insertion direction is defined as the longitudinal direction, the direction parallel to the imaginary line connecting the pair of through holes when viewed from the release direction is defined as the orthogonal direction, the direction perpendicular to the insertion direction and the longitudinal direction respectively, the circulating part is composed of a divisible first part and a second part, the dividing line separating the first part and the second part overlaps the return path when viewed from the orthogonal direction, the first part is, A ball screw device comprising: a first main body portion that constitutes a part of the main body portion; a pair of first legs that constitute a part of the leg portion; a second part comprising: a second main body portion that constitutes the remainder of the main body portion and is positioned relative to the first main body portion in the detachment direction; a pair of second legs that constitute the remainder of the leg portion and is positioned relative to the first legs portion in the longitudinal direction; the direction in which the return path extends is defined as the return path direction; a projection is formed at the end of the first part in the return path direction, projecting outward from the first legs portion in the longitudinal direction; the projection extends along the inner circumferential surface of the through hole and abuts against the inner circumferential surface of the through hole from the inside in the longitudinal direction; an opening is formed at the end of the first part in the return path direction, surrounded by the first legs portion and the projection; and the end face of the second part in the return path direction faces the detachment direction face of the projection. (2) The ball screw device according to (1), wherein the pair of protrusions press the inner circumferential surfaces of the pair of through holes outward in the longitudinal direction by elastic deformation.(3) The ball screw device according to (1) or (2), having a sleeve fitted to the outer circumference of the nut, wherein the second component is in contact with the inner circumference of the sleeve. (4) The ball screw device according to (3), wherein the sleeve presses the second component in the insertion direction, the second component presses the first component in the insertion direction, and the first component is pressed against the outer circumference of the nut. (5) The ball screw device according to any one of (1) to (4), wherein a housing portion for housing the circulating component is formed on the outer circumference of the nut, and the second component is press-fitted into the housing portion. (6) The ball screw device according to any one of (1) to (4), wherein a housing portion for housing the circulating component is formed on the outer circumference of the nut, and the second component is press-fitted into the housing portion. (7) The ball screw device according to any one of (1) to (4), wherein a housing portion for housing the circulating part is formed on the outer circumferential surface of the nut, and at least one protrusion is formed on the second part that protrudes toward the inner surface of the housing portion, and the protrusion is flattened between the second part and the inner surface of the housing portion. (8) The ball screw device according to any one of (1) to (7), wherein one end of the protrusion is connected to the first leg portion, and the other end of the protrusion is not connected to the first leg portion. (9) The ball screw device according to any one of (1) to (7), wherein both ends of the protrusion are connected to the first leg portion. (10) The ball screw device according to any one of (1) to (7), wherein the protrusion has two longitudinal protrusions that extend linearly in the longitudinal direction and are spaced apart from each other in the orthogonal direction, and an orthogonal protrusion that extends linearly in the orthogonal direction and is connected to the outer ends of the two longitudinal protrusions in the longitudinal direction. (11) The ball screw device according to any one of (1) to (7), wherein the projection has two partial projections divided into two in the orthogonal direction, and the inner end of each partial projection in the longitudinal direction is connected to the first leg. (12) The ball screw device according to any one of (1) to (11), wherein a fitting groove into which the projection fits is formed on the inner circumferential surface of the through hole.(13) The ball screw device according to any one of (1) to (12), wherein the first component has a first opposing surface facing the second component, and the first opposing surface has a groove surface formed on it with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction. (14) The ball screw device according to (13), wherein the second component has a second opposing surface facing the first component, and the second opposing surface has a groove surface formed on it with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction. (15) The ball screw device according to any one of (1) to (12), wherein the first component has a first opposing surface facing the second component, and the second component has a second opposing surface facing the first component, and the first opposing surface has a surface formed on it with a cross-sectional shape that is straight when cut in a direction perpendicular to the return path direction, and the second opposing surface has a groove surface formed on it with a cross-sectional shape that is U-shaped when cut in a direction perpendicular to the return path direction. (16) The ball screw device according to any one of (1) to (15), wherein the first component is made of metal and manufactured by deep drawing, punching, pressing, or metal powder injection molding. (17) The ball screw device according to any one of (1) to (15), wherein the first component is made of resin and manufactured by resin injection molding. (18) The ball screw device according to any one of (1) to (15), wherein the second component is made of metal and manufactured by deep drawing, punching, pressing, or metal powder injection molding. (19) The ball screw device according to any one of (1) to (15), wherein the second component is made of resin and manufactured by resin injection molding.

[0097] 100 Ball screw device 1 Screw shaft 2 Nut 3 Ball 4 Circulation part 5 Sleeve 10 Outer circumference raceway surface 21 Outer circumference surface 22 Inner circumference raceway surface 30 Housing part 31 Through hole 32 Recess 33 Inner circumference surface 34 Seat surface 35 Bottom surface 40 Return path 41 Leg part 42 Main body part 43 End face 44 Opening 45 Tongue 50, 50A, 50B, 50C, 50F First part 51 First leg part 52 First main body part 55, 55A, 55B, 55C Protruding part 60, 60E, 60F Second part 61 Second leg part 62 Second main body part 69 Protrusion 70 Dividing line 71 First opposing surface 72 Second opposing surface 133 Fitting groove 155 Longitudinal projection 156 Orthogonal projection 255 Partial projection

Claims

1. The circulating part comprises a screw shaft, a nut into which the screw shaft is inserted, a plurality of balls arranged in a track between the screw shaft and the nut, and a tubular circulating part having a return path formed inside and openings formed on both end faces, wherein the nut has a pair of through holes that penetrate the outer and inner surfaces of the nut, the circulating part has a pair of legs inserted into the pair of through holes, and a main body that connects the pair of legs, the insertion direction is parallel to the through holes and the direction in which the legs are inserted into the through holes is defined as the removal direction, the longitudinal direction is parallel to the imaginary line connecting the pair of through holes when viewed from the removal direction, and the orthogonal direction is perpendicular to the insertion direction and the longitudinal direction, the circulating part is composed of a divisible first part and a second part, the dividing line separating the first part and the second part extends in the longitudinal direction when viewed from the orthogonal direction, and the first part is, A ball screw device comprising: a first main body portion that constitutes a part of the main body portion; a pair of first legs that constitute a part of the leg portion; a second part comprising: a second main body portion that constitutes the remainder of the main body portion and is positioned relative to the first main body portion in the detachment direction; a pair of second legs that constitute the remainder of the leg portion and is positioned relative to the first legs portion in the longitudinal direction; the direction in which the return path extends is defined as the return path direction; a projection is formed at the end of the first part in the return path direction, projecting outward from the first legs portion in the longitudinal direction; the projection extends along the inner circumferential surface of the through hole and abuts against the inner circumferential surface of the through hole from the inside in the longitudinal direction; an opening is formed at the end of the first part in the return path direction, surrounded by the first legs portion and the projection; and the end face of the second part in the return path direction faces the detachment direction face of the projection.

2. The ball screw device according to claim 1, wherein the pair of protrusions press the inner circumferential surfaces of the pair of through holes outward in the longitudinal direction by elastic deformation.

3. The ball screw device according to claim 1 or claim 2, having a sleeve that fits onto the outer circumference of the nut, wherein the second component is in contact with the inner surface of the sleeve.

4. The ball screw device according to claim 3, wherein the sleeve presses the second component in the insertion direction, the second component presses the first component in the insertion direction, and the first component is pressed against the outer circumference of the nut.

5. The ball screw device according to any one of claims 1 to 4, wherein a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut, and the second component is press-fitted into the housing portion.

6. The ball screw device according to any one of claims 1 to 4, wherein a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut, and the second component is fitted into the housing portion with a gap.

7. The ball screw device according to any one of claims 1 to 4, wherein a housing portion for housing the circulating component is formed on the outer circumferential surface of the nut, and at least one convex portion is formed on the second component that protrudes toward the inner surface of the housing portion, and the convex portion is crushed between the second component and the inner surface of the housing portion.

8. The ball screw device according to any one of claims 1 to 7, wherein one end of the protrusion is connected to the first leg, and the other end of the protrusion is not connected to the first leg.

9. The ball screw device according to any one of claims 1 to 7, wherein both ends of the protruding portion are connected to the first leg portion.

10. The ball screw device according to any one of claims 1 to 7, wherein the projection comprises two longitudinal projections extending linearly in the longitudinal direction and spaced apart from each other in the orthogonal direction, and an orthogonal projection extending linearly in the orthogonal direction and connecting to the outer ends of the two longitudinal projections in the longitudinal direction.

11. The ball screw device according to any one of claims 1 to 7, wherein the projection has two partial projections divided into two in the orthogonal direction, and the inner end of each partial projection in the longitudinal direction is connected to the first leg.

12. The ball screw device according to any one of claims 1 to 11, wherein a fitting groove into which the protruding portion fits is formed on the inner circumferential surface of the through hole.

13. The ball screw device according to any one of claims 1 to 12, wherein the first component has a first opposing surface facing the second component, and the first opposing surface has a groove surface formed thereon with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction.

14. The ball screw device according to claim 13, wherein the second part has a second opposing surface facing the first part, and the second opposing surface has a groove surface formed thereon with a cross-sectional shape that is semicircular when cut in a direction perpendicular to the return path direction.

15. The ball screw device according to any one of claims 1 to 12, wherein the first component has a first opposing surface facing the second component, the second component has a second opposing surface facing the first component, the first opposing surface has a surface formed on it with a straight cross-sectional shape when cut in a direction perpendicular to the return path direction, and the second opposing surface has a grooved surface formed on it with a U-shaped cross-sectional shape when cut in a direction perpendicular to the return path direction.

16. The ball screw device according to any one of claims 1 to 15, wherein the first component is made of metal and manufactured by drawing, punching, pressing, or metal powder injection molding.

17. The ball screw device according to any one of claims 1 to 15, wherein the first component is made of resin and manufactured by resin injection molding.

18. The ball screw device according to any one of claims 1 to 15, wherein the second component is made of metal and manufactured by drawing, punching, pressing, or metal powder injection molding.

19. The ball screw device according to any one of claims 1 to 15, wherein the second component is made of resin and manufactured by resin injection molding.

Images