Ball screw device

Abstract

A ball screw device includes a screw shaft, a nut, a plurality of balls, a circulation member, a base member, and a fixing member. The nut is provided with a through hole penetrating in the assembly direction. The circulation member has a cylindrical portion, a leg portion, and a curved portion. The base member has a main body portion extending along the cylindrical portion and the curved portion. The main body part has a groove-shaped seat surface. The cross-sectional shape of the seat surface is arc-shaped about the center line of the cylindrical portion and the two curved portions. An arc-shaped support surface is formed at a portion of the seat surface that is in contact with the cylindrical portion, and the support surface opens in a direction opposite to the assembly direction when viewed from a rotation axis direction parallel to a center line of the cylindrical portion. An arcuate restricting surface is formed at a portion of the seat surface that is in contact with the bent portion, and the restricting surface is open to the side where the through-hole is located when viewed from the assembly direction. The restricting surface has a first restricting portion that comes into contact with the bent portion from the first rotational direction and a second restricting portion that comes into contact with the bent portion from the second rotational direction.

Description

Technical Field

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

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

[0003] As an example of a circulation component, there is a tubular member as shown in Patent Document 1. The tubular circulation component includes: a cylindrical portion extending along the outer peripheral surface of the nut; a bent portion bent from the cylindrical portion; and a leg portion extending from the bent portion. The leg portion is inserted into a through hole that penetrates the outer peripheral surface and the inner peripheral surface of the nut. And, the ball is picked up from the track by the front end of the leg portion, or the ball is returned to the track from the front end of the leg portion.

[0004] However, the through hole of the nut is through in the direction of assembling the circulation component to the nut (hereinafter referred to as the assembly direction). In addition, the leg of patent document 1 also extends in the assembly direction. That is, the leg and the through hole extend in the same direction, and the leg is engaged with the through hole. According to this engagement, the rotation of the leg around the cylindrical part is restricted. Hereinafter, the rotation around the cylindrical part is sometimes referred to as rotation.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-269564 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] In recent years, a circulation component that scoops up the ball from the tangential direction relative to the track is being developed. The leg of the circulation component is tilted relative to the assembly direction of the circulation component. In other words, the leg is not engaged with the through hole, and the leg is easy to rotate. If the leg rotates, the front end position of the leg is offset, and it is impossible to smoothly scoop up and return the ball.

[0010] The present disclosure has been made in view of the above-mentioned circumstances, and an object of the present disclosure is to provide a ball screw device that suppresses positional deviation of a leg portion in a rotation direction.

[0011] Solutions for solving problems

[0012] In order to achieve the above-mentioned purpose, a ball screw device of a technical solution of the present disclosure comprises: a screw shaft; a nut through which the screw shaft passes; a plurality of balls arranged between the screw shaft and the nut; a circulation component having a circular cross-sectional shape, which circulates the balls; a base component arranged between the outer peripheral surface of the nut and the circulation component; and a fixing component, which clamps the circulation component with the base component. Two through holes are provided in the nut, and the two through holes penetrate the nut in the assembly direction of assembling the circulation component to the outer peripheral surface of the nut. The circulation component has: a cylindrical portion, which is cylindrical and arranged on the outer peripheral side of the nut; two legs, which are inserted into the through holes; and two curved portions, which connect the cylindrical portion and the legs. The base component has a main body extending along the cylindrical portion and the two curved portions. The main body has a groove-shaped seat surface overlapping the cylindrical portion and the two curved portions. The cross-sectional shape of the seat surface is in an arc shape with the center line of the cylindrical portion and the two curved portions as the center. The portion of the seat surface that abuts against the cylindrical portion forms an arc-shaped supporting surface, which is open in the direction opposite to the assembly direction when viewed from the direction of the rotation axis parallel to the center line of the cylindrical portion. The portion of the seat surface that abuts against the curved portion forms an arc-shaped limiting surface, which is open in the direction pointed to by the end of the main body portion when viewed from the assembly direction. The limiting surface has: a first limiting portion, which abuts against the curved portion from a first rotation direction centered on the center line of the cylindrical portion; and a second limiting portion, which abuts against the curved portion from a second rotation direction opposite to the first rotation direction.

[0013] According to the present disclosure, when the circulation component is assembled to the nut, the bent portion abuts against the first limiting portion and the second limiting portion. Thereby, it is avoided that the bent portion is assembled in a state of being rotated in the first rotation direction or the second rotation direction. As a result, the positional deviation of the leg connected to the bent portion in the rotation direction can be suppressed. In addition, the conventional cylindrical portion is clamped by the outer peripheral surface of the nut and the fixing component. The outer peripheral surface of the conventional nut is a plane, and the fixing force relative to the circulation component is small. In addition, if the ball rolls in the circulation component, the circulation component vibrates, causing wear of the circulation component. On the other hand, the cylindrical portion of the present disclosure is supported on an arc-shaped seat surface. That is, the contact area between the base component and the cylindrical portion is increased, and the fixing force of the fixed cylindrical portion is higher. Therefore, it is not easy to generate vibration of the circulation component, and the wear of the circulation component can be suppressed.

[0014] In addition, as a desired technical solution of the ball screw device of one technical solution of the present disclosure, a recessed portion is provided on the outer peripheral surface of the nut and at the edge of the through hole to avoid contact with the two curved portions. The base component has two engaging portions protruding from the end of the main body toward the assembly direction and engaging with the recessed portion.

[0015] According to the structure, it is avoided that the main body and the circulation part are assembled in a state where the position is offset along the outer peripheral surface of the nut. In other words, the positioning accuracy of the leg is improved. In addition, the recess is used as a position for the interlocking part to be interlocked. Accordingly, it is not necessary to form a recess for the interlocking part to be interlocked, which can avoid the strength reduction of the nut.

[0016] In addition, as a desired technical solution of the ball screw device of one technical solution of the present disclosure, the fitting portion has an inner side surface facing the through hole when viewed from the assembly direction, the seat surface extends to the inner side surface, and the fitting portion abuts against the curved portion or the leg portion.

[0017] According to the above structure, the number of places supporting the bent portion or the leg increases, thereby improving the positioning accuracy of the leg.

[0018] Furthermore, as a desirable aspect of the ball screw device according to one aspect of the present disclosure, the base member is made of resin.

[0019] According to the structure, the main body can be assembled to the nut in a compressed state by applying a load by the fixing member. Therefore, even if the cylindrical portion of the circulation member is worn, no gap will be generated between the cylindrical portion and the main body. Therefore, the clamping force generated by the fixing member and the base member is sustained for a long time. As described above, it is not easy to generate vibration in the circulation member and cause the circulation member to wear.

[0020] In addition, as a desired technical solution of the ball screw device according to one technical solution of the present disclosure, the two leg portions extend in a tangential direction relative to a track between the nut and the screw shaft.

[0021] In addition, as a desirable technical aspect of the ball screw device according to one technical aspect of the present disclosure, the main body is provided with a through hole penetrating the main body.

[0022] When the base member is exposed to high temperature, the main body thermally expands in the longitudinal direction. In addition, the limiting surface of the main body presses the bent parts in a direction away from each other. On the other hand, the main body receives a reaction force from the two bent parts being pressed. As a result, the main body is deformed in a manner that the through hole is flattened. As described above, it is possible to avoid a situation where the thermally expanded main body presses the bent parts and causes the front end position of the leg to shift.

[0023] In addition, as a desirable technical solution of the ball screw device according to one technical solution of the present disclosure, the main body has two divided main body parts formed by dividing a central part in a longitudinal direction of the main body, and a gap is provided between the two divided main body parts.

[0024] When the divided body portion thermally expands, the divided body portion extends toward the gap between the two divided body portions. Therefore, it is possible to avoid a situation where the thermally expanded body portion presses the bent portion and the position of the front end of the leg portion is displaced.

[0025] According to the above structure, the scooping up of the balls and the returning of the balls are made smooth.

[0026] Effects of the Invention

[0027] According to the ball screw device of the present disclosure, it is possible to suppress positional deviation of the leg portion in the rotation direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram when the ball screw device according to the first embodiment is viewed from the assembly direction of the circulation components.

[0029] Figure 2 This is an exploded perspective view showing a state in which a nut, a base member, and a circulation member are extracted and disassembled from the ball screw device according to the first embodiment.

[0030] Figure 3 This is a diagram showing the nut of Embodiment 1 as viewed from the assembling direction.

[0031] Figure 4 It is a figure which shows the assembly state of the base member and the circulation member with respect to the nut in Embodiment 1.

[0032] Figure 5 In implementation mode 1, Figure 4 The arrow V points in the direction of the diagram when looking at the base component and the circulation component.

[0033] Figure 6 yes Figure 1 Sectional view taken along line VI-VI.

[0034] Figure 7 yes Figure 1 Cross-sectional view taken along line VII-VII.

[0035] Figure 8 This is a top view of the base assembly as viewed from the assembly direction.

[0036] Fig. 9 It is a cross-sectional view when the base component is cut along the center line.

[0037] Fig.10 yes Figure 8 Sectional view along line XX.

[0038] Fig.11 yes Figure 8 Cross-sectional view taken along line XI-XI.

[0039] Fig.12 yes Fig. 9 Cross-sectional view along line XII-XII.

[0040] Fig.13 This is a perspective view of the base member of Modification 1 as viewed from an angle from the assembling direction.

[0041] Fig.14 This is a diagram of the base member of Modification 2 viewed from the assembling direction.

[0042] Fig.15 This is a side view of the base member of Modification 2 as viewed from the side.

[0043] Fig.16 This is a diagram of the base member of Modification 3 viewed from the assembling direction. DETAILED DESCRIPTION

[0044] The embodiments for implementing the invention are described in detail with reference to the accompanying drawings. The present invention is not limited to the contents described in the following description. In addition, the structural elements described below include elements that can be easily thought of by those skilled in the art, and substantially the same elements. Moreover, the structural elements described below can be appropriately combined.

[0045] (Implementation Method 1)

[0046] Figure 1 This is a diagram when the ball screw device according to the first embodiment is viewed from the assembly direction of the circulation components. Figure 2 This is an exploded perspective view showing a state in which a nut, a base member, and a circulation member are extracted and disassembled from the ball screw device according to the first embodiment. Figure 3 This is a diagram showing the nut of Embodiment 1 as viewed from the assembling direction. Figure 4 It is a figure which shows the assembly state of the base member and the circulation member with respect to the nut in Embodiment 1. Figure 5 In implementation mode 1, Figure 4 The arrow V points in the direction of the diagram when looking at the base component and the circulation component. Figure 6 yes Figure 1 Sectional view taken along line VI-VI. Figure 7 yes Figure 1 Cross-sectional view taken along line VII-VII. Figure 8 This is a top view of the base assembly as viewed from the assembly direction. Fig. 9 It is a cross-sectional view when the base component is cut along the center line. Fig.10 yes Figure 8 Sectional view along line XX. Fig.11 yes Figure 8 Cross-sectional view taken along line XI-XI. Fig.12 yes Fig. 9 Cross-sectional view along line XII-XII.

[0047] like Figure 1 As shown, the ball screw device 100 of the first embodiment includes a screw shaft 1, a nut 2, and a plurality of balls 3 (see Figure 6 ), a circulation member 4, a fixing member 5 and a base member 6. In the following description, the direction parallel to the screw shaft 1 is referred to as an axial direction.

[0048] The screw shaft 1 is a solid rod-shaped member. An outer peripheral raceway surface 10 is provided on the outer peripheral surface of the screw shaft 1. The nut 2 is a cylindrical member. An inner peripheral raceway surface 20 is provided on the inner peripheral surface of the nut 2 (see Figure 2 The screw shaft 1 passes through the nut 2, and the outer raceway surface 10 and the inner raceway surface 20 face each other. Between the outer raceway surface 10 and the inner raceway surface 20 is a spiral raceway 7 for the balls 3 to roll (see Figure 6 ).

[0049] The outer peripheral surface 21 of the nut 2 is cut in a D shape. Therefore, the outer peripheral surface 21 has a plane 22 and an arc surface 23 that is arc-shaped (roughly C-shaped) when viewed from the axial direction. The plane 22 is the surface on which the circulation component 4 is set. Therefore, the direction parallel to the perpendicular line of the plane 22 and close to the plane 22 is the direction in which the circulation component 4 is assembled to the nut 2 (refer to Figure 2 Arrow A. Hereinafter, referred to as assembly direction A).

[0050] Two ridges 24 extending in the axial direction are provided at the boundary between the plane 22 and the arc surface 23. Hereinafter, the direction in which the ridges 24 extend is referred to as the length direction X of the plane 22. In addition, the direction parallel to the plane 22 and orthogonal to the length direction X of the plane 22 is referred to as the width direction Y of the plane 22. The nut 2 is provided with two through holes 25 penetrating the outer peripheral surface 21 and the inner peripheral surface of the nut 2.

[0051] In addition, in this embodiment, the two through holes 25, the circulation component 4, the fixing component 5 and the base component 6 are viewed from the assembly direction A at the point P of the plane 22 (see Figure 1 ) is a point-symmetrical shape based on the plane 22. Point P of the plane 22 is an arbitrary point on the plane 22. Therefore, any one of the circulation component 4, the fixed component 5 and the base component 6 can be assembled to the nut 2 even in a state of rotating around the point P of the plane 22. Therefore, in the following description, the structure on one side relative to the point P is described as a representative example, and the description of the structure on the other side relative to the point P is omitted.

[0052] like Figure 2 As shown, the through hole 25 is formed by cutting the outer peripheral surface 21 of the nut 2 from the assembly direction A. That is, the through hole 25 extends along the assembly direction A (refer to Figure 5 , Figure 6 ). In addition, in the present disclosure, the through-hole forming method may be a processing method other than cutting.

[0053] like Figure 3 As shown, the through hole 25 crosses the ridge line 24 and penetrates the plane 22 and the arc surface 23. In addition, the through hole 25 is longer in the width direction Y of the plane 22 than in the length direction X of the plane 22. Thus, the leg 42 of the circulation member 4 can be arranged in the through hole 25 in a state inclined in the width direction Y of the plane 22.

[0054] A recess 26 is provided on the outer peripheral surface 21 of the nut 2 and at the edge of the through hole 25, which is recessed toward the inner peripheral side of the nut 2. The recess 26 is used to prevent the nut 2 from contacting the curved portion 43 of the circulation component 4 (see Figure 6 ). In addition, Figure 6 In order to facilitate the viewing of the recessed portion 26, the fitting portion 61 of the base member 6 disposed in the recessed portion 26 is omitted. In addition, the recessed portion 26 is provided with an arc-shaped fitting surface 28. In addition, two internal threaded holes 29 for screwing the screws 59 for mounting the fixing member 5 are provided on the plane 22.

[0055] The circulation member 4 is a cylindrical member, and the inner space thereof is a return path 40 (see Figure 7 ).like Figure 4 , Figure 5 As shown, the circulation member 4 includes a cylindrical portion 41 disposed on the outer peripheral side of the nut 2 , two leg portions 42 inserted into the through hole 25 , and two bent portions 43 connecting the cylindrical portion 41 and the leg portions 42 .

[0056] The cross-sectional shapes of the cylindrical portion 41, the leg portion 42, and the curved portion 43 are all circular (see Figure 7 ). Hereinafter, a line continuously connecting the centers of the cross-sectional shapes (circular shapes) of the cylindrical portion 41, the leg portion 42, and the curved portion 43 will be referred to as a center line M of the circulation component 4. In the first embodiment, the circulation component 4 is manufactured by bending a metal cylindrical component by press working.

[0057] In addition, the circulation component 4 of the first embodiment is made of metal, but the present disclosure may also be a circulation component made of resin. In addition, in the present disclosure, when the circulation component 4 is manufactured from a metal cylindrical component, its processing method is not limited to stamping. In addition, the circulation component 4 of the first embodiment is formed by a single component, but the present disclosure may also be a circulation component formed by joining multiple components.

[0058] The center line M41 of the cylindrical portion 41 is a straight line. That is, the cylindrical portion 41 is cylindrical. In addition, the above-mentioned "rotation" refers to the rotation around the center line M41 of the cylindrical portion 41. Hereinafter, the direction parallel to the center line M41 is referred to as the rotation axis direction. In addition, regarding the rotation direction around the center line M41, one side is referred to as the first rotation direction L1, and the other side is referred to as the second rotation direction L2 (refer to Fig.10 , Fig.11 ).

[0059] like Figure 6 As shown, the center line M42 of the leg 42 is substantially straight. Therefore, the leg 42 is substantially cylindrical. The leg 42 is arranged in the through hole 25. The center line M42 of the leg 42 is inclined relative to the assembly direction A. Therefore, the leg 42 is a shape that cannot be fitted into the through hole 25.

[0060] A lifting portion 42a for lifting the ball 3 from the track 7 is provided at the front end of the leg 42. The center line M42 of the leg 42 is a tangent to a pitch circle C formed by connecting the centers of the balls 3 rolling on the track 7. Thus, the ball 3 can be smoothly lifted from the front end of the leg 42 or returned.

[0061] like Figure 5 As shown, the center line M43 of the curved portion 43 is Figure 4 The shape of the curved portion 43 is an arc (quarter circle) when viewed in the direction of the arrow V. Therefore, when the ball 3 rolls in the curved portion 43, the direction of travel of the ball 3 changes by approximately 90°. Figure 6 As shown, a portion of the bent portion 43 is disposed in the recessed portion 26 of the nut 2 .

[0062] like Figure 7 As shown in the figure, the fixing member 5 includes a suppressing portion 50 and two fastened portions 51. The cross-sectional shape of the suppressing portion 50 includes an arc portion 52 that is arc-shaped along the outer peripheral surface of the cylindrical portion 41, and two wall portions 53 that extend linearly from the ends of the arc portion 52 toward the assembly direction A. The fastened portion 51 is fastened to the flat surface 22 by a screw 59. As a result, the cylindrical portion 41 is pressed against the main body 60 of the base member 6. In addition, in the present embodiment, the main body 60 of the base member 6 is assembled in a compressed and deformed state by the fastening of the screw 59.

[0063] The base member 6 of the first embodiment is a resin product. Figure 5 As shown, the base member 6 includes a main body portion 60 extending along the plane 22 of the nut 2 and two fitting portions 61 protruding in the assembly direction A from both ends of the main body portion 60 .

[0064] like Figure 8 As shown in FIG. 1 , when viewed from the assembly direction A, the main body 60 extends between the two through holes 25. Therefore, the direction in which the main body 60 extends is inclined relative to the ridgeline 24 (the length direction X of the plane 22). Hereinafter, the direction in which the main body 60 extends is referred to as the length direction Z. In addition, the direction parallel to the plane 22 and orthogonal to the length direction Z of the main body 60 is referred to as the width direction W of the main body 60.

[0065] like Fig. 9 As shown, the main body 60 has: a bottom surface 62, which faces the assembly direction A; and a seat surface 63, which is provided on a surface facing the direction opposite to the bottom surface 62. The bottom surface 62 is flat and abuts against the flat surface 22 of the nut 2 (refer to Figure 5 ).

[0066] The seat surface 63 is a concave surface (arc surface) open toward the circulation component 4. The seat surface 63 extends from one end of the main body 60 to the other end and is in a groove shape. Fig. 9 As shown in FIG. 1 , the bottom (most concave portion) 63a of the seat surface 63 extends in a direction parallel to the plane 22 at the center of the longitudinal direction Z of the main body 60. On the other hand, the bottom 63a of the seat surface 63 is curved so as to approach the plane 22 as it goes toward the end of the main body 60. Therefore, the seat surface 63 is divided into a portion that is linear in the longitudinal direction Z of the main body 60 and a portion that is curved in the longitudinal direction Z of the main body 60. Hereinafter, the portion that is linear in the seat surface 63 is referred to as a support surface 70. The portion that is curved in the seat surface 63 is referred to as a restriction surface 71.

[0067] like Figure 7 As shown, the support surface 70 overlaps with the cylindrical portion 41. Furthermore, the support surface 70 and the fixing member 5 cooperate to clamp the cylindrical portion 41. The cross-sectional shape of the support surface 70 is an arc shape centered on the center line M41 of the cylindrical portion 41. Therefore, the cylindrical portion 41 is supported by the main body 60 in a manner that does not cause positional displacement in the width direction W of the main body 60.

[0068] like Figure 5As shown, the limiting surface 71 overlaps with the curved portion 43 and abuts against the curved portion 43. In addition, since the limiting surface 71 is curved, the range in which the limiting surface 71 abuts against the curved portion 43 is not a part of the direction in which the curved portion 43 extends, but abuts within a certain length range. Moreover, the two curved portions 43 abut against each other in a manner of sandwiching the two limiting surfaces 71 from the length direction Z of the main body 60. Therefore, the circulation component 4 is supported by the main body 60 in a manner that does not cause positional displacement in the length direction Z of the main body 60. In addition, in the present embodiment, the limiting surface 71 is also provided on the fitting portion 61. Therefore, after the description of the fitting portion 61, the details of the limiting surface 71 are described.

[0069] like Figure 8 As shown, the fitting portion 61 is arranged in the recess 26. The fitting portion 61 has an outer side surface 65 opposite to the fitting surface 28 of the recess 26. The outer side surface 65 is arc-shaped and has the same shape as the fitting surface 28. Therefore, the fitting portion 61 is fitted into the recess 26. In addition, by this fitting, the main body 60 is assembled to the nut 2 in a manner that does not cause positional deviation in the direction parallel to the plane 22.

[0070] When viewed from the assembly direction A, the fitting portion 61 is a shape in which a portion of the circular shape is cut away. The cut away portion is a range overlapping with the through hole 25 when viewed from the assembly direction A. Hereinafter, the cut away portion is referred to as the inner side surface 66. The seat surface 63 (limiting surface 71) of the main body 60 is provided on the inner side surface 66 of the fitting portion 61. In other words, the seat surface 63 is extended to the inner side surface 66 of the fitting portion 61. In addition, the inner side surface 66 (seat surface 63, limiting surface 71) of the fitting portion 61 abuts against the outer peripheral surface of the curved portion 43.

[0071] Next, the restriction surface 71 is described in detail. The restriction surface 71 includes two restriction surfaces: the restriction surface 71 provided in the fitting portion 61 and the restriction surface 71 located at the end of the main body 60. For convenience of description, the restriction surface 71 provided in the fitting portion 61 will be described first.

[0072] like Figure 8 As shown in FIG. 1 , the restriction surface 71 provided on the fitting portion 61 is in an arc shape with the center line M43 of the curved portion 43 as the center. Therefore, when viewed from the assembly direction A, the restriction surface 71 provided on the fitting portion 61 is open to the side where the through hole 25 (leg portion 42) is arranged. In addition, the restriction surface 71A of one fitting portion 61 and the restriction surface 71B of the other fitting portion 61 of the two fitting portions 61 are open in opposite directions to each other.

[0073] like Fig.10As shown, the limiting surface 71A abuts against the outer peripheral surface of the curved portion 43 in an arc shape across the center line M42 and the center line M43 when viewed from the rotation axis direction. That is, the limiting surface 71A has a first limiting portion 72 abutting from the first rotation direction L1 and a second limiting portion 73 abutting from the second rotation direction L2, with the center line M42 and the center line M43 as a dividing line. Therefore, the rotation (position shift) of the curved portion 43 in the first rotation direction L1 is limited by the first limiting portion 72. In addition, the rotation (position shift) of the curved portion 43 in the second rotation direction L2 is limited by the second limiting portion 73.

[0074] The first limiting portion 72 is a portion of the limiting surface 71A that is disposed closer to the first rotation direction L1 than the dividing line (center line M42 and center line M43). The second limiting portion 73 is a portion of the limiting surface 71A that is disposed closer to the second rotation direction L2 than the dividing line (center line M42 and center line M43). Figure 8 , Fig.10 As shown, in the limiting surface 71A, the length in the circumferential direction of the second limiting portion 73 abutting against the curved portion 43 is greater than the length in the circumferential direction of the first limiting portion 72 abutting against the curved portion 43. In other words, in the limiting surface 71A, the supporting force of the second limiting portion 73 supporting the curved portion 43 is greater than the supporting force of the first limiting portion 72 supporting the curved portion 43.

[0075] On the other hand, Fig.11 As shown, regarding the limiting surface 71B provided in the other fitting portion 61, in terms of the length in the circumferential direction in contact with the curved portion 43, the first limiting portion 72 arranged closer to the first rotation direction L1 than the dividing line (center line M42 and center line M43) is longer than the second limiting portion 73 arranged closer to the second rotation direction L2 than the dividing line (center line M42 and center line M43). That is, in the limiting surface 71B, the supporting force of the first limiting portion 72 supporting the curved portion 43 is greater than the supporting force of the second limiting portion 73 supporting the curved portion 43. Therefore, the supporting force generated by the limiting surface 71 is uniform and does not deviate to one side of the rotation direction.

[0076] In addition, if Fig.12 As shown in FIG. 1 , the limiting surface 71 provided at the end of the main body 60 is in an arc shape with the center line M42 of the curved portion 43 as the center. That is, in the limiting surface 71 located at the end of the main body 60, the first limiting portion 72 abutting from the first rotation direction L1 and the second limiting portion 73 abutting from the second rotation direction L2 are also provided with the center line M42 as the dividing line. Therefore, the rotation of the curved portion 43 can also be limited by the limiting surface 71 provided at the main body 60.

[0077] As described above, although the cross-sectional shape of the seat surface 63 is the same shape (arc shape) with the center line M of the circulation component 4 as the center, the support surface 70 and the limiting surface 71 are opened in different directions due to the different objects of abutment (cylindrical portion 41 or curved portion 43). In other words, the support surface 70 limits the positional deviation of the cylindrical portion 41 in the width direction W of the main body 60, and the limiting surface 71 limits the positional deviation of the curved portion 43 in the rotation direction.

[0078] Next, the effect of the ball screw device 100 of the present embodiment 1 is described. Before assembling the circulation component 4, the base component 6 is arranged on the plane 22 of the nut 2. At this time, the two fitting parts 61 of the base component 6 are fitted into the recessed part 26 of the nut 2. Thus, the base component 6 is assembled to the nut 2 in a manner that does not cause positional displacement in a direction parallel to the plane 22.

[0079] Next, assemble the circulation component 4. Insert the circulation component 4 and the leg portion 42 of the circulation component 4 into the through hole 25. At this time, the cylindrical portion 41 and the two curved portions 43 are arranged in a manner overlapping with the seat surface 63 of the base component 6. Accordingly, the cylindrical portion 41 is supported on the supporting surface 70, and the positional deviation in the width direction W of the main body 60 is suppressed. In addition, the two curved portions 43 abut against the two limiting surfaces 71, and the positional deviation in the length direction Z of the main body 60 is suppressed. As described above, the circulation component 4 is assembled to the base component 6 in a manner that does not cause positional deviation in the direction parallel to the plane 22.

[0080] In addition, the bent portion 43 contacts the limiting surface 71, and the positional deviation in the rotational direction is suppressed. Therefore, the positional deviation of the leg portion 42 in the rotational direction is also suppressed. As a result, the front end of the leg portion 42 is arranged at a predetermined assembly position, and the ball 3 can be smoothly scooped up or returned.

[0081] In addition, the support surface 70 has the same shape as the outer peripheral surface of the cylindrical portion 41, and contacts the outer peripheral surface of the cylindrical portion 41 without a gap. In the past, the cylindrical portion was clamped by the flat surface 22 of the nut 2 and the fixing member 5, but according to the present embodiment, which is clamped by the support surface 70 and the fixing member 5, the friction force with respect to the cylindrical portion 41 is large. Therefore, compared with the past, the fixing force of the cylindrical portion 41 is larger. As a result, the circulation member 4 is not easy to vibrate, and the wear of the circulation member 4 is suppressed.

[0082] Furthermore, even if the cylindrical portion 41 of the circulation member 4 is worn, no gap is generated between the fixed member 5 and the base member 6. In other words, even if the outer peripheral surface of the cylindrical portion 41 is reduced in diameter due to wear, no gap is generated due to the elastic deformation of the main body 60 that is compressed and deformed. Therefore, the clamping force generated by the fixed member 5 and the base member 6 is sustained for a long time.

[0083] Furthermore, the recessed portion 26 is used as a portion into which the fitting portion 61 fits in order to avoid contact with the bent portion 43. This eliminates the need to form a separate recessed portion into which the fitting portion 61 fits, and reduces the strength of the nut 2.

[0084] According to the above, the ball screw device 100 of the first embodiment includes: a screw shaft 1; a nut 2 through which the screw shaft 1 passes; a plurality of balls 3 arranged between the screw shaft 1 and the nut 2; a circulation member 4 having a circular cross-sectional shape, the circulation member 4 circulates the balls 3; a base member 6 arranged between the outer peripheral surface 21 of the nut 2 and the circulation member 4; and a fixing member 5, the circulation member 4 being clamped by the fixing member 5 and the base member 6. The nut 2 is provided with two through holes 25, which penetrate the nut 2 in the assembly direction A of assembling the circulation member 4 to the outer peripheral surface 21 of the nut 2. The circulation member 4 has: a cylindrical portion 41, which is cylindrical and arranged on the outer peripheral side of the nut 2; two leg portions 42, which are inserted into the through holes 25; and two bent portions 43, which connect the cylindrical portion 41 and the leg portions 42. The base member 6 has a main body 60 extending along the cylindrical portion 41 and the two curved portions 43. The main body 60 has a groove-shaped seat surface 63 overlapping the cylindrical portion 41 and the two curved portions 43. The cross-sectional shape of the seat surface 63 is arc-shaped with the center line M41 of the cylindrical portion 41 and the center line M43 of the two curved portions 43 as the center. The portion of the seat surface 63 that abuts against the cylindrical portion 41 forms an arc-shaped support surface 70, which is open in the direction opposite to the assembly direction A when viewed from the direction of the rotation axis parallel to the center line M41 of the cylindrical portion 41. The portion of the seat surface 63 that abuts against the curved portion 43 forms an arc-shaped restriction surface 71, which is open to the side where the through hole 25 is arranged when viewed from the assembly direction A. The limiting surface 71 includes a first limiting portion 72 that contacts the curved portion 43 in a first rotation direction L1 centered on the center line M41 of the cylindrical portion 41 and a second limiting portion 73 that contacts the curved portion 43 in a second rotation direction L2 opposite to the first rotation direction L1.

[0085] According to the ball screw device 100 of the first embodiment, the leg portion 42 does not shift in the rotation direction. In addition, the fixing force for fixing the circulation member 4 is high, and wear of the circulation member 4 is suppressed.

[0086] In the first embodiment, the recess 26 is provided on the outer peripheral surface 21 of the nut 2 and at the edge of the through hole 25 to avoid contact with the two bent portions 43. The base member 6 has two fitting portions 61 protruding from the end of the body 60 in the assembly direction A and fitting into the recess 26.

[0087] According to the first embodiment, the circulation member 4 does not shift in position in the direction parallel to the flat surface 22 of the nut 2. In addition, a decrease in the strength of the nut 2 can be avoided.

[0088] Furthermore, in the first embodiment, the fitting portion 61 has the inner side surface 66 facing the through hole 25 when viewed from the assembling direction A. The seat surface 63 is extended to the inner side surface 66. The fitting portion 61 abuts against the bent portion 43 or the leg portion 42.

[0089] According to the first embodiment, the base member 6 has more portions that come into contact with the bent portion 43 or the leg portion 42. Therefore, it is possible to more reliably suppress positional deviation of the leg portion 42 in the rotation direction.

[0090] Furthermore, in Embodiment 1, the base member 6 is made of resin.

[0091] According to the first embodiment, the base member 6 can be assembled in a state compressed in the assembly direction A. Therefore, even if the cylindrical portion 41 is worn, no gap is generated between the fixing member 5 and the base member 6 .

[0092] Furthermore, in the first embodiment, the two leg portions 42 extend in the tangential direction with respect to the track 7 between the screw shaft 1 and the nut 2 .

[0093] According to the first embodiment, the scooping up of the balls 3 and the returning of the balls 3 are made smooth.

[0094] Embodiment 1 is described above, but the present disclosure is not limited to the example described in Embodiment 1. For example, the base member 6 may not be made of a resin material, but may be made of a metal material such as brass that is softer than the nut 2 and the circulation member 4. If the base member is made of a soft metal material, it will be compressed under the load from the fixing member 5. In addition, when the cylindrical portion 41 is worn, the base member made of a soft metal material is deformed, and no gap is generated between the fixing member 5 and the base member 6. Therefore, the same effect as the resin base member 6 of Embodiment 1 can be exerted.

[0095] In addition, the present disclosure may include glass fibers extending in the longitudinal direction Z of the main body 60 inside the resin main body 60. This makes the base member 6 less susceptible to thermal expansion. Therefore, the difference in linear expansion coefficient with the metal nut 2 is reduced, and creep deformation is suppressed.

[0096] In addition, the base component of the present disclosure can also be made of materials other than the above-mentioned resin material and soft metal material. Even such a base component can exert the same effect as that of the first embodiment, and can suppress the position deviation of the leg 42 in the rotation direction and the position deviation in the direction parallel to the plane 22. In addition, the fixing force of the fixed circulation component 4 is high, and the wear of the circulation component 4 can also be suppressed.

[0097] In addition, in the circulation component 4 of the first embodiment, the leg 42 is inclined relative to the assembly direction A, but the circulation component 4 of the present disclosure may also be a circulation component in which the leg 42 is parallel to the assembly direction A (the leg 42 can be fitted into the through hole 25). Even in such a circulation component, a gap may be generated between the leg 42 and the through hole 25 due to manufacturing errors. Therefore, according to the base component of the present disclosure, it is possible to support the leg 42 and suppress the positional deviation of the leg 42 in the rotation direction.

[0098] Next, a base member of a modified example will be described. In the following description, differences from the first embodiment will be focused on.

[0099] (Variant 1)

[0100] Fig.13 This is a three-dimensional view of the base member of Modification Example 1 viewed from an oblique angle from the assembly direction. Fig.13 As shown, the base member 6A of the modification example 1 is different from the base member 6 of the embodiment 1 in that it does not have the fitting portion 61. According to such a base member 6A, the positional deviation of the bent portion 43 and the leg portion 42 in the rotational direction is restricted by the restriction surface 71 (71A, 71B) provided at the end of the main body 60. In addition, the fixing force of the fixed circulation member 4 is high, and the wear of the circulation member 4 can also be suppressed. However, since the base member 6A is not positioned, there is a possibility that the circulation member 4 supported by the base member 6 is positionally deviated in a direction parallel to the plane 22 of the nut 2.

[0101] (Variant 2)

[0102] Fig.14 This is a diagram of the base member of Modification 2 viewed from the assembling direction. Fig.15 This is a side view of the base member of Modification Example 2 as viewed from the side. Fig.14 , Fig.15 As shown, the base member 6B of the second modification is different from the base member 6 of the first embodiment in that a circular through hole 75 is provided. The through hole 75 penetrates the main body 60 in a direction parallel to the assembly direction A. That is, it penetrates a part of the support surface 70 (seat surface 63).

[0103] According to the base component 6B of the second modification, when the ball screw device 100 is used, when the base component 6B is exposed to high temperature, the main body 60 thermally expands in the longitudinal direction Z. As a result, the base component 6B presses the two curved portions 43 that abut against the limiting surface 71 in directions away from each other. In addition, the main body 60 receives a reaction force from the two curved portions 43, and the main body 60 is deformed in a manner that the through hole 75 is flattened. Therefore, according to the second modification, the positional deviation of the curved portion 43 caused by the thermal expansion of the base component 6B can be suppressed.

[0104] In addition, although the through hole 75 of the modification 2 is circular, the present disclosure is not limited thereto. In addition, a plurality of through holes 75 may be provided.

[0105] (Variant 3)

[0106] Fig.16 This is a view of the base member of Modification 3 viewed from the assembly direction. Fig.16 As shown in FIG. 1 , the base member 6C of the modification 3 is different from the base member 6 of the embodiment 1 in that the main body 60 is divided into two. The main body 60 has two divided main body parts 76 divided at the center of the main body 60 in the longitudinal direction Z. In addition, the length of the main body 60 in the longitudinal direction obtained by combining the two divided main body parts 76 is shorter than that of the main body 60 of the embodiment 1. That is, a gap S is generated between the two divided main body parts 76.

[0107] According to the base member 6C of the above-described modification 3, when the divided body portion 76 thermally expands, it expands so as to reduce the gap S. Therefore, it is possible to suppress positional deviation of the bent portion 43 .

[0108] Description of Reference Numerals

[0109] 100. Ball screw device; 1. Screw shaft; 2. Nut; 3. Ball; 4. Circulation component; 5. Fixed component; 6. Base component; 21. Outer peripheral surface; 22. Plane; 25. Through hole; 26. Recess; 40. Return path; 41. Cylindrical portion; 42. Leg; 43. Bend; 60. Main body; 61. Fitting portion; 63. Seat surface; 66. Inner side surface; 70. Support surface; 71. 71A, 71B. Limiting surface; 72. First limiting portion; 73. Second limiting portion; 75. Through hole; 76. Split main body; M, M41, M42, M43, center line.

Claims

1. A ball screw device, comprising: Screw shaft; A nut, through which the screw shaft passes; A plurality of balls disposed between the screw shaft and the nut; A circulation component, the cross-section of which is circular, and the circulation component circulates the balls; A base member disposed between the outer peripheral surface of the nut and the circulation member; as well as A fixing component is used to clamp the circulation component with the base component. The nut is provided with two through holes, the two through holes penetrating the nut in an assembling direction for assembling the circulation component to the outer peripheral surface of the nut, The circulation component has: A cylindrical portion having a cylindrical shape and arranged on the outer peripheral side of the nut; two legs inserted into the through holes; as well as two curved portions connecting the cylindrical portion and the leg portion, The base member has a main body extending along the cylindrical portion and the two curved portions. The main body has a groove-shaped seat surface overlapping the cylindrical portion and the two curved portions. The cross-sectional shape of the seat surface is an arc shape with the center line of the cylindrical portion and the two curved portions as the center. The portion of the seat surface that contacts the cylindrical portion forms an arc-shaped support surface, and the support surface is open in a direction opposite to the assembly direction when viewed from the rotation axis direction parallel to the center line of the cylindrical portion. The portion of the seat surface that contacts the bent portion forms an arc-shaped limiting surface, and the limiting surface is open to the side where the through hole is arranged when viewed from the assembly direction. The limiting surface has: a first restricting portion that abuts against the curved portion in a first rotation direction centered on the center line of the cylindrical portion; and The second restricting portion contacts the curved portion in a second rotational direction which is opposite to the first rotational direction.

2. The ball screw device according to claim 1, in, A recessed portion is provided on the outer peripheral surface of the nut and at the edge of the through hole to avoid contact with the two bent portions. The base member has two fitting portions that protrude from an end portion of the main body portion in the assembling direction and fit into the recessed portions.

3. The ball screw device according to claim 2, in, The fitting portion has an inner side surface facing the through hole when viewed from the assembling direction, The seat surface is extended to the inner side surface, The fitting portion abuts against the bent portion or the leg portion.

4. The ball screw device according to claim 1, in, The base member is made of resin.

5. The ball screw device according to claim 1, in, The two legs extend in a tangential direction relative to a track between the nut and the screw shaft.

6. The ball screw device according to any one of claims 1 to 5, in, The main body is provided with a through hole penetrating the main body.

7. The ball screw device according to any one of claims 1 to 5, in, The main body has two divided main body parts formed by dividing the central part in the longitudinal direction of the main body. A gap is provided between the two divided main body parts.

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