Ball screw device

Abstract

The present invention provides a ball screw device having anti-loosening components applicable to both axial sides of the screw shaft or both axial sides of the nut. [Solution] The ball screw device comprises a screw shaft with an outer circumferential raceway surface formed on its outer circumferential surface, a nut into which the screw shaft is inserted and which has an inner circumferential raceway surface formed on its inner circumferential surface, a plurality of balls arranged in a raceway between the outer circumferential raceway surface and the inner circumferential raceway surface, and an annular anti-loosening component viewed from the axial direction parallel to the central axis of the screw shaft. One of the screw shaft and the nut has a circulation section. The other of the screw shaft and the nut has an opening that opens the outer circumferential raceway surface or the inner circumferential raceway surface in the axial direction, and an annular housing groove that is recessed radially from the outer circumferential surface of the screw shaft or the inner circumferential surface of the nut. The anti-loosening component is a spiral ring that can expand and contract in diameter by elastic deformation. The spiral ring fits into the housing groove and closes the opening from the axial direction.

Description

Technical Field

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

Background Art

[0002] A ball screw device is a device that converts rotational motion into linear motion, or converts linear motion into rotational motion. Such a ball screw device includes a screw shaft, a nut into which the screw shaft is inserted on the inner peripheral side, and a plurality of balls disposed between the screw shaft and the nut. An outer peripheral raceway surface is formed on the outer peripheral surface of the screw shaft. An inner peripheral raceway surface facing the outer peripheral raceway surface is formed on the inner peripheral surface of the nut. The space between the outer peripheral raceway surface and the inner peripheral raceway surface constitutes a raceway, and the plurality of balls are disposed in this raceway. Here, when the amount of movement of the screw shaft in the axial direction increases, the outer peripheral raceway surface and the inner peripheral raceway surface no longer face each other. For this reason, the balls fall out from between the screw shaft and the nut. Hereinafter, preventing the balls from falling out may be referred to as ball drop prevention.

[0003] In order to achieve ball drop prevention, in the following patent document, the screw thread disposed at one axial end portion of the screw shaft is caulked. The caulked portion constitutes a caulking portion that reduces the groove width of the outer peripheral raceway surface. Then, when the amount of movement of the screw shaft toward the other side in the axial direction increases, the caulking portion comes into contact with the balls. Thereby, the movement of the screw shaft toward the other side in the axial direction is restricted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the screw shaft and nut undergo heat treatment during the manufacturing process to obtain the desired hardness. Therefore, the crimped portion described in the above-mentioned patent document must be formed before the heat treatment. In other words, it is difficult to form crimped portions on both ends of the screw shaft (or nut) after the ball screw device has been assembled. On the other hand, if crimped portions are formed on both ends of the screw shaft (or nut) before the heat treatment, the ball screw device cannot be assembled. For these reasons, the crimped portion described in the above-mentioned patent document can only be formed on one side in the axial direction of the screw shaft (or nut). For these reasons, there is a need for a component that can prevent the balls from falling out (hereinafter referred to as a ball-fall prevention component) and that can be applied to both sides in the axial direction of the screw shaft (or nut).

[0006] This disclosure has been made in view of the above, and aims to provide a ball screw device having a bolt-on prevention component applicable to both axial sides of the screw shaft or both axial sides of the nut. [Means for solving the problem]

[0007] To achieve the above objective, a ball screw device according to one aspect of the present disclosure comprises a screw shaft having an outer peripheral raceway surface formed on its outer peripheral surface, a nut into which the screw shaft is inserted on its inner peripheral side and which has an inner peripheral raceway surface formed on its inner peripheral surface, a plurality of balls arranged in a raceway between the outer peripheral raceway surface and the inner peripheral raceway surface, and an annular anti-loosening component viewed from an axial direction parallel to the central axis of the screw shaft. One of the screw shaft and the nut has a circulation portion. The other of the screw shaft and the nut has an opening that causes the outer peripheral raceway surface or the inner peripheral raceway surface to open in the axial direction, and an annular housing groove that is recessed radially from the outer peripheral surface of the screw shaft or the inner peripheral surface of the nut. The anti-loosening component is a spiral ring that can expand and contract in diameter by elastic deformation. The spiral ring fits into the housing groove and closes the opening from the axial direction.

[0008] According to this disclosure, if the screw shaft has a housing groove, after assembling the ball screw device, the spiral ring is elastically deformed to expand its diameter. Then, the screw shaft is inserted into the inner circumference of the spiral ring. Next, the force applied to the spiral ring is removed, and the spiral ring is fitted into the housing groove. This integrates the spiral ring with the screw shaft. On the other hand, if the nut has a housing groove, after assembling the ball screw device, the spiral ring is elastically deformed to reduce its diameter. Then, the spiral ring is inserted into the inner circumference of the nut. Next, the force applied to the spiral ring is removed, and the spiral ring is fitted into the housing groove. This integrates the spiral ring with the nut. Then, the screw shaft moves relative to the nut in the axial direction, and as the amount of movement increases, the spiral ring comes into contact with the ball. This restricts further relative movement of the screw shaft, thus preventing loosening. Also, because the spiral ring is annular, it closes the opening even when rotated. Furthermore, the loosening prevention component of this disclosure can be attached to the screw shaft or nut after assembling the ball screw device. Therefore, it can be applied to both sides of the screw shaft in the axial direction or to both sides of the nut in the axial direction.

[0009] Furthermore, in the ball screw device of this disclosure, the nut has the circulation portion. The screw shaft has a screw shaft body having the outer peripheral raceway surface, and a projection portion projecting from the end face of the screw shaft body. The end face has an opening formed by cutting out a part of the circumferential direction, causing the outer peripheral raceway surface to open in the axial direction. The outer peripheral surface of the projection portion has a receiving groove that is recessed radially inward. The inner diameter of the spiral ring at its natural length is smaller than the outer diameter of the projection portion. The spiral ring is capable of elastic deformation with an inner diameter larger than the outer diameter of the projection portion.

[0010] According to the above configuration, the spiral ring is attached to the screw shaft.

[0011] Furthermore, in the ball screw device of this disclosure, the diameter of the bottom surface of the housing groove is larger than the inner diameter of the spiral ring at its natural length.

[0012] According to the above configuration, the ball release prevention component abuts against the bottom surface of the housing groove, and there is no gap between the ball release member and the bottom surface. Therefore, the radial movement of the ball release prevention component is restricted. In addition, a restoring force (a force that tries to reduce the diameter) acts on the ball release prevention component fitted into the housing groove, causing it to return to its original shape. The ball release prevention component has a large frictional force (normal force to the bottom surface) on its bottom surface, which restricts its axial movement and rotation. As a result, the ball release prevention component does not generate contact noise with the inner surface of the housing groove. Furthermore, wear of the ball release prevention component is suppressed.

[0013] Furthermore, in the ball screw device of this disclosure, the outer diameter of the spiral ring attached to the housing groove is less than or equal to the diameter of the circle connecting the centers of the plurality of balls arranged in the track.

[0014] According to the above configuration, the anti-loosening component is less likely to come into contact with the inner circumferential surface of the nut or with the circulating component provided on the nut.

[0015] Furthermore, in the ball screw device of this disclosure, the outer diameter of the spiral ring attached to the housing groove is less than or equal to the outer diameter of the screw shaft body.

[0016] According to the above configuration, the anti-loosening component does not protrude radially outward from the outer circumferential surface of the screw shaft body. Therefore, contact between the anti-loosening component and the inner circumferential surface of the nut or the circulating component provided on the nut is avoided.

[0017] Furthermore, in the ball screw device of this disclosure, the outer peripheral raceway surface is Gothic arc shaped, and the outer diameter of the spiral ring attached to the housing groove is greater than the diameter of the circle formed by connecting the contact points between the outer peripheral raceway surface and the ball.

[0018] According to the above configuration, when the ball-lock prevention component comes into contact with the ball, there is a low possibility that the ball will go over the ball-lock prevention component.

[0019] Furthermore, in the ball screw device of this disclosure, the outer diameter of the protrusion is less than or equal to the diameter of the groove bottom of the outer peripheral raceway surface.

[0020] If the outer circumferential surface of the protrusion protrudes radially outward from the groove bottom of the outer raceway surface, then when forming the outer raceway surface by through-feed rolling, the die will come into contact with the outer circumferential surface of the protrusion, making it impossible to form the outer raceway surface. Similarly, when forming the outer raceway surface by through-feed grinding, the grinding wheel will come into contact with the outer circumferential surface of the protrusion, making it impossible to form the outer raceway surface. On the other hand, with the above configuration, neither the die nor the grinding wheel comes into contact with the protrusion. Therefore, through-feed machining becomes possible.

[0021] Furthermore, in the ball screw device of this disclosure, a center hole is formed in the center of the end face of the protruding portion.

[0022] When assembling a spiral ring to the protruding part of a screw shaft, it is advisable to use a jig. Specifically, the jig is used in contact with the end face of the protruding part. The jig is also frustoconical in shape; that is, the outer surface of the jig expands in diameter toward the other axial direction. The jig is then inserted into the inner circumference of the spiral ring. Next, the spiral ring is moved axially along the outer surface of the jig, causing the spiral ring to expand radially outward due to the outer surface of the jig. As the amount of movement of the spiral ring increases, the component positioned on the inner circumference of the spiral ring switches from the jig to the protruding part, and the spiral ring fits into the outer circumference of the protruding part. Finally, the spiral ring is moved along the outer circumference of the protruding part and fitted into the housing groove, completing the installation of the spiral ring. Here, if the central axis of the jig and the central axis of the screw shaft do not coincide, when a component positioned on the inner circumference of the spiral ring switches from the jig to the protruding part, the spiral ring will catch on the end face of the protruding part. According to the above configuration, a projection is provided on the end face of the jig facing the other direction in the axial direction. Furthermore, the projection is positioned on the central axis of the jig. Moreover, when the projection is fitted into the center hole, the jig and the screw shaft are positioned coaxially. Thus, the spiral ring catching on the end face of the protruding part is avoided. In other words, according to the above configuration, it becomes easy to position the screw shaft and the jig coaxially.

[0023] Further, in the ball screw device of the present disclosure, the protruding portion includes a first protruding portion protruding from one end surface of the screw shaft main body, and a second protruding portion protruding from the other end surface of the screw shaft main body. The burr prevention component may include a first burr prevention component fitted into the accommodation groove of the first protruding portion, and a second burr prevention component fitted into the accommodation groove of the second protruding portion.

[0024] Further, in the ball screw device of the present disclosure, the protruding portion has a first protruding portion protruding from one end surface of the screw shaft main body. The burr prevention component has a first burr prevention component fitted into the accommodation groove of the first protruding portion. A caulking portion formed by caulking a thread is formed at the other axial end of the screw shaft main body. A part of the outer peripheral raceway surface may have a groove width reduced by the caulking portion.

[0025] Further, in the ball screw device of the present disclosure, the screw shaft has the circulation portion. The nut includes an annular nut main body having the inner peripheral raceway surface, and an annular annular portion protruding from an end surface of the nut main body. The end surface is formed with the opening that is notched at a part in the circumferential direction and opens the inner peripheral raceway surface in the axial direction. The inner peripheral surface of the annular portion is formed with the accommodation groove recessed radially outward. The outer diameter of the spiral ring at the natural length is larger than the inner diameter of the annular portion. The spiral ring can be elastically deformed to have an outer diameter smaller than the inner diameter of the annular portion.

[0026] According to the above configuration, the spiral ring is attached to the nut.

[0027] Further, in the ball screw device of the present disclosure, the diameter of the bottom surface of the accommodation groove is smaller than the outer diameter of the spiral ring at the natural length.

[0028] According to the above configuration, the ball release prevention component abuts against the bottom surface of the housing groove, and there is no gap between the ball release member and the bottom surface. In other words, the radial movement of the ball release prevention component is restricted. In addition, a restoring force (a force that tries to expand the diameter) acts on the ball release prevention component fitted into the housing groove, causing it to return to its original shape. The ball release prevention component has a large frictional force (normal force to the bottom surface) on its bottom surface, which restricts its axial movement and rotation. As a result, the ball release prevention component does not produce contact noise with the inner surface of the housing groove. Furthermore, wear of the ball release prevention component is suppressed.

[0029] Furthermore, in the ball screw device of this disclosure, the inner diameter of the spiral ring attached to the housing groove is greater than or equal to the diameter of the circle connecting the centers of the plurality of balls arranged in the track.

[0030] According to the above configuration, the anti-loosening component is less likely to come into contact with the outer surface of the screw shaft or with the circulating component provided on the screw shaft.

[0031] Furthermore, in the ball screw device of this disclosure, the inner diameter of the spiral ring attached to the housing groove is greater than or equal to the inner diameter of the nut body.

[0032] According to the above configuration, the anti-loosening component does not protrude radially inward from the inner circumferential surface of the nut body. Therefore, contact between the anti-loosening component and the outer circumferential surface of the screw shaft or the circulating component provided on the screw shaft is avoided.

[0033] Furthermore, in the ball screw device of this disclosure, the inner circumferential raceway surface is Gothic arc shaped. The inner diameter of the spiral ring attached to the housing groove is smaller than the diameter of the circle formed by connecting the contact points between the inner circumferential raceway surface and the ball.

[0034] According to the above configuration, when the ball-lock prevention component comes into contact with the ball, there is a low possibility that the ball will go over the ball-lock prevention component.

[0035] Furthermore, in the ball screw device of the present disclosure, the annular portion has a first annular portion protruding from one end face of the nut body and a second annular portion protruding from the other end face of the nut body. The anti-loosening component may have a first anti-loosening component that fits into the housing groove of the first annular portion and a second anti-loosening component that fits into the housing groove of the second annular portion.

[0036] Furthermore, in the ball screw device of this disclosure, the annular portion has a first annular portion that protrudes from one end face of the nut body. The anti-loosening component has a first anti-loosening component that fits into the housing groove of the first annular portion. A crimped portion formed by crimping a screw thread is formed at the other axial end of the nut body. The groove width of a part of the inner circumferential raceway surface may be reduced by the crimped portion. [Effects of the Invention]

[0037] According to the ball screw device of this disclosure, the anti-loosening component can be applied to both sides of the screw shaft in the axial direction or to both sides of the nut in the axial direction. [Brief explanation of the drawing]

[0038] [Figure 1] Figure 1 is a cross-sectional view of the ball screw device of Embodiment 1, cut in the axial direction. [Figure 2] Figure 2 is an enlarged view of the screw shaft body and protruding portion of Embodiment 1. [Figure 3] Figure 3 is a view of the screw shaft of Embodiment 1 from the first direction. [Figure 4] Figure 4 is a perspective view of the anti-bulging component (spiral ring) of Embodiment 1. [Figure 5] Figure 5 is a view of the anti-loosening component (spiral ring) of Embodiment 1 from the axial direction. [Figure 6] Figure 6 is an enlarged view of the spiral ring attached to the screw shaft in Embodiment 1. [Figure 7]Figure 7 is a cross-sectional view (viewed along the line VII-VII in Figure 3) of the ball screw device of Embodiment 1 (with the screw shaft moved in the second direction) cut in the axial direction. [Figure 8] Figure 8 is a cross-sectional view showing the process of attaching a spiral ring to the screw shaft of Embodiment 1. [Figure 9] Figure 9 is a cross-sectional view of the ball screw device of Modification 1, cut in the axial direction. [Figure 10] Figure 10 is a cross-sectional view of the ball screw device of the modified example 2, cut in the axial direction. [Figure 11] Figure 11 is a cross-sectional view of the ball screw device of Modification 3, cut in the axial direction. [Figure 12] Figure 12 is a magnified view of the nut and spiral ring of the modified example 3. [Figure 13] Figure 13 is a cross-sectional view of the ball screw device of Modification 3 (with the nut moved in the second direction) cut in the axial direction. [Modes for carrying out the invention]

[0039] The forms for implementing this disclosure 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 are readily conceivable to a person skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate.

[0040] (Embodiment 1) Figure 1 is a cross-sectional view of the ball screw device of Embodiment 1, cut in the axial direction. As shown in Figure 1, the ball screw device 100 of Embodiment 1 comprises a screw shaft 1, a nut 2, a plurality of balls 3 (not shown in Figure 1; see Figure 7), a plurality of links 4, a sleeve 5, and a release prevention component (first release prevention component) 6. Hereinafter, the direction parallel to the central axis O1 of the screw shaft 1 will be referred to as the axial direction. The direction perpendicular to the central axis O1 will be referred to as the radial direction.

[0041] The screw shaft 1 is a cylindrical component centered on a central axis O1. The screw shaft 1 comprises a screw shaft body 10, a protruding portion (first protruding portion) 30, and a connecting portion 31. The screw shaft body 10 is located in the axial center of the screw shaft 1. The protruding portion 30 is located on one side of the axial direction relative to the screw shaft body 10. The connecting portion 31 is located on the other side of the axial direction relative to the screw shaft body 10. Hereinafter, the axial direction on which the protruding portion 30 is located, as viewed from the screw shaft body 10, will be referred to as the first direction X1. The axial direction on which the connecting portion 31 is located, as viewed from the screw shaft body 10, will be referred to as the second direction X2.

[0042] The outer diameter of the screw shaft body 10 is formed to be R10. An outer circumferential raceway surface 12 is formed on the outer circumferential surface 11 of the screw shaft body 10. The outer circumferential raceway surface 12 is a surface that is recessed radially inward from the outer circumferential surface 11 of the screw shaft body 10 and extends in a helical manner. In this embodiment, the outer circumferential raceway surface 12 has a Gothic arc shape. However, in this disclosure, the outer circumferential raceway surface 12 may also have a circular arc shape.

[0043] Figure 2 is an enlarged view of the screw shaft body and protrusion of Embodiment 1. As shown in Figure 2, a groove bottom 13, which is the most radially inward recessed part of the outer circumferential raceway surface 12, is located in the widthwise center of the outer circumferential raceway surface 12. The diameter of this groove bottom 13 is formed as R13.

[0044] As shown in Figure 1, the outer circumferential raceway surface 12 extends from the end in the first direction X1 to the end in the second direction X2 of the outer circumferential surface 11 of the screw shaft body 10. In other words, the outer circumferential raceway surface 12 is formed on the entire outer circumferential surface 11 of the screw shaft body 10.

[0045] The screw shaft body 10 has a first end face 15 facing a first direction X1 and a second end face 16 facing a second direction X2. The first end face 15 and the second end face 16 are planes perpendicular to the central axis O1.

[0046] Figure 3 is a view of the screw shaft of Embodiment 1 from a first direction. A first opening 17 is formed on the first end face 15, which cuts out a portion of the circumferential direction. The first opening 17 opens the outer circumferential raceway surface 12 in the first direction X1. A second opening 18 is also formed on the second end face 16, which opens the outer circumferential raceway surface 12 in the second direction X2 (see Figure 1).

[0047] As shown in Figure 3, the projection 30 is formed in a cylindrical shape with respect to the central axis O1. A center hole 33 is formed on the end face 32 of the projection 30 in the first direction X1. The center hole 33 is a hole used when rotating the material of the screw shaft 1 to process the material, and is located coaxially with the central axis O1 of the screw shaft 1.

[0048] As shown in Figure 2, the outer diameter of the protrusion 30 is R30. This outer diameter R30 of the protrusion 30 is smaller than the diameter R13 of the groove bottom 13. In addition, an annular receiving groove 35 that is recessed radially inward is formed on the outer circumferential surface 34 of the protrusion 30. This receiving groove 35 is a groove for accommodating the anti-loosening component 6 on the outer circumferential side.

[0049] The inner surface of the accommodating groove 35 has a first side surface 36 positioned in a first direction X1 relative to the accommodating groove 35, a bottom surface 37, and a second side surface 38 positioned in a second direction X2 relative to the accommodating groove 35. The diameter of the bottom surface 37 is formed as R37. The accommodating groove 35 is located at the end of the outer circumferential surface 34 of the protruding portion 30 in the second direction X2. Therefore, the second side surface 38 is formed by the first end surface 15.

[0050] As shown in Figure 1, the connecting portion 31 is a part for connecting to other parts. For example, when the screw shaft 1 is moving linearly, a piston or the like is fitted into the connecting portion 31. On the other hand, when the screw shaft 1 is moving rotationally, a bearing device that rotatably supports the screw shaft 1 or a part for transmitting torque to the screw shaft 1 is fitted into the connecting portion 31.

[0051] Furthermore, examples of components for transmitting torque to the screw shaft 1 include reduction devices such as carriers in a planetary gear mechanism and driven pulleys in a pulley mechanism, but this disclosure is not limited to those exemplified. Also, although the connecting portion 31 is cylindrical, a male spline portion, for example, may be formed on the connecting portion 31, and the shape of the connecting portion 31 is not limited. In addition, although the screw shaft 1 in the embodiment has a connecting portion 31, this disclosure may also describe a screw shaft that does not have a connecting portion 31.

[0052] The outer diameter of the connecting portion 31 is R31. The outer diameter R31 of the connecting portion 31 is smaller than the diameter R13 of the groove bottom 13 (Figure 2). Therefore, although the protrusion 30 and the connecting portion 31 are arranged on both axial sides of the screw shaft body 10, the outer diameter R30 of the protrusion 30 (see Figure 2) and the outer diameter R31 of the connecting portion 31 (Figure 1) are smaller than the diameter R13 of the groove bottom 13 (see Figure 2). For this reason, even if the outer circumferential raceway surface 12 is formed by through-feed rolling, the die will not come into contact with the protrusion 30 and the connecting portion 31. Alternatively, even if the outer circumferential raceway surface 12 is formed by through-feed grinding, the grinding wheel will not come into contact with the protrusion 30 and the connecting portion 31. In other words, the screw shaft 1 has a shape that can be processed by through-feed machining and is excellent for mass production.

[0053] As shown in Figure 1, the nut 2 is a cylindrical component centered on a central axis O1. The nut 2 consists only of a nut body 25, on which an inner circumferential raceway surface 21 is formed on the inner circumference. The inner diameter of the nut body 25 is formed as R2. A through hole 22 is formed in the inner circumferential surface 20 of the nut body 25. The inner circumferential raceway surface 21 is a surface that is recessed radially outward from the inner circumferential surface 20 of the nut body 25 and extends in a spiral shape. In this embodiment, the inner circumferential raceway surface 21 has a Gothic arc shape. However, this disclosure may also describe an inner circumferential raceway surface 21 with a circular arc shape. The inner circumferential raceway surface 21 is radially opposite to the outer circumferential raceway surface 12. The space between the inner circumferential raceway surface 21 and the outer circumferential raceway surface 12 constitutes a raceway 7. Multiple balls 3 (see Figure 7) are arranged in the raceway 7.

[0054] The through hole 22 penetrates the inner circumferential surface 20 and the outer circumferential surface 23 of the nut body 25. A ball 4 is inserted into the through hole 22. A circulation groove surface 40 is formed on the radially inner surface of the ball 4, recessed radially outward. The circulation groove surface 40 extends in a counter-spiral direction opposite to the spiral direction in which the inner circumferential raceway surface 21 extends, and connects the two ends of the inner circumferential raceway surface 21. As a result, a ball 3 (see Figure 7) that has moved from one end of the raceway 7 to the other circulates back to the one end of the raceway 7.

[0055] In this embodiment, a spool 4 is used as the circulation part for circulating the balls 3, but this disclosure is not limited to this. For example, the circulation groove surface 40 may be formed on the inner circumferential surface 20 of the nut body 25 (nut 2) by forging or cutting the inner circumferential surface 20. Alternatively, it may be a tube and a deflector, and there are no particular restrictions on the type of circulation part.

[0056] The sleeve 5 is a cylindrical component that fits onto the outer surface 24 of the nut body 25 (nut 2). The sleeve 5 then contacts the nut 4 from the radially outer side. This prevents the nut 4 from falling out radially outward through the through hole 22.

[0057] Figure 4 is a perspective view of the ball-loosening prevention component (spiral ring) of Embodiment 1. Figure 5 is a view of the ball-loosening prevention component (spiral ring) of Embodiment 1 from the axial direction. The ball-loosening prevention component 6 is a component for preventing the ball 3 from falling out. As shown in Figures 4 and 5, the ball-loosening prevention component 6 is a spiral ring 60. The spiral ring 60 is a wire 61 formed into a spiral shape by winding it around a rod-shaped core. The wire 61 in Embodiment 1 is a flat wire with a square cross-section. However, the wire in this disclosure may also be a round wire with a circular cross-section, and there are no particular restrictions on the type of wire 61.

[0058] The spiral ring 60 has a wire 61 that makes approximately 1.8 turns when it is at its natural length. Therefore, the distance L1 (see Figure 5) between one end 62 and the other end 63 of the wire 61 when it is at its natural length is approximately 0.2 turns. Also, when viewed from the axial direction, the intermediate portion 64 of the wire 61 is located between the one end 62 and the other end 63. For this reason, the spiral ring 60 is annular when viewed from the axial direction.

[0059] The spiral ring 60 of Embodiment 1 is formed by tight winding. Tight winding is a method of winding the wire 61 around a core material to form a spiral shape, while ensuring that the wire 61 is tightly in contact with adjacent parts in the axial direction without any gaps. Therefore, each part of the wire 61 is tightly in contact with other parts of the wire 61 adjacent to it in the axial direction. The inner diameter of the spiral ring 60 at its natural length is R60 (see Figure 5). The outer diameter of the spiral ring 60 at its natural length is R160 (see Figure 5).

[0060] Figure 6 is an enlarged view of the spiral ring attached to the screw shaft in Embodiment 1. As shown in Figure 6, the spiral ring 60 is attached to the screw shaft 1 by fitting it to the outer circumference of the housing groove 35. Hereinafter, the spiral ring 60 in the state fitted to the outer circumference of the housing groove 35 will be referred to as the fitted spiral ring 60.

[0061] The inner diameter R60 of the spiral ring 60 at its natural length (see Figure 5) is smaller than the outer diameter R30 of the protrusion 30 (see Figure 2). Therefore, when attaching the spiral ring 60 to the screw shaft 1, the spiral ring 60 is elastically deformed to expand in diameter, and the protrusion 30 is inserted into the inside of the spiral ring 60. Then, the force applied to the spiral ring 60 is removed, and the spiral ring 60 is reduced in diameter. By this procedure, the spiral ring 60 can be fitted into the housing groove 35. Furthermore, in this disclosure, a jig 200 may be used when attaching the spiral ring 60. The method of attaching the spiral ring 60 using the jig 200 will be described later.

[0062] The diameter R37 of the bottom surface 37 of the housing groove 35 (see Figure 2) is larger than the inner diameter R60 of the spiral ring 60 at its natural length (see Figure 5). Therefore, the inner diameter of the spiral ring 60 when fitted is expanded compared to its natural length. Thus, the inner circumference of the spiral ring 60 is in contact with the bottom surface 37 of the housing groove 35 without any gaps. As a result, radial movement of the spiral ring 60 is suppressed. Furthermore, a restoring force (a force that tries to shrink the diameter) acts on the spiral ring 60, causing it to return to its original shape. Therefore, the frictional force (normal force against the bottom surface 37) between the spiral ring 60 and the bottom surface 37 is large, suppressing axial movement and rotation.

[0063] Furthermore, when fitted, the spiral ring 60 has a greater distance L1 between one end 62 and the other end 63 of the wire 61 than it does at its natural length. If the wire 61 is short, the expansion of the spiral ring 60's diameter may result in a C-shape rather than an annular shape when viewed from the axial direction. In other words, a gap may occur between the one end 62 and the other end 63 of the wire 61. However, the wire 61 in this embodiment is relatively long, at approximately 1.8 turns at its natural length. Therefore, even when fitted, the wire 61 extends for more than one turn, and the spiral ring 60 has an annular shape when viewed from the axial direction.

[0064] As shown in Figure 6, the outer diameter of the spiral ring 60 when fitted is larger than the outer diameter R160 (see Figure 5) at its natural length, and is R61. The outer diameter R61 of the spiral ring 60 when fitted is smaller than the inner diameter R2 (see Figure 1) of the nut 2. Therefore, the spiral ring 60 can be positioned on the inner circumference side of the nut 2. Also, the R61 of the spiral ring 60 is slightly smaller than the outer diameter R10 (see Figure 1) of the screw shaft body 10. For this reason, the spiral ring 60 does not protrude radially outward from the outer circumferential surface 11 of the screw shaft body 10.

[0065] The spiral ring 60 is in contact with the first end face 15 (second side surface 38). As a result, the spiral ring 60 closes the first opening 17 from the first direction X1.

[0066] Furthermore, the axial size M2 of the spiral ring 60 is slightly smaller than the axial size M1 of the housing groove 35. Therefore, it is easier to fit the spiral ring 60 into the housing groove 35 than if the size M2 of the spiral ring 60 and the size M1 of the housing groove 35 were the same. In addition, a minute gap M3 is created between the spiral ring 60 and the first side surface 36. This minute gap M3 is the difference between the axial size M1 of the housing groove 35 and the axial size M2 of the spiral ring 60.

[0067] Figure 7 is a cross-sectional view (viewed along the line VII-VII in Figure 3) of the ball screw device of Embodiment 1 (with the screw shaft moved in the second direction) cut in the axial direction. Next, we will explain the case where the screw shaft 1 moves in the second direction X2 relative to the nut 2. The raceway 7 located closest to the first direction X1 among the multiple raceways 7 will be referred to as the first raceway 7a.

[0068] As shown in Figure 7, when the screw shaft 1 moves in the second direction X2, the spiral ring 60 is positioned on the inner circumference side of the nut 2. Furthermore, since the spiral ring 60 does not protrude radially outward from the outer circumferential surface 11 of the screw shaft body 10, it does not come into contact with the threads (inner circumferential surface 20) of the nut 2 or the nut 4.

[0069] Furthermore, as the amount of movement by the screw shaft 1 in the second direction X2 increases, and the ball 3 on the first track 7a attempts to pass through the first opening 17, the ball 3 comes into contact with the spiral ring 60. As a result, the spiral ring 60 catches on the ball 3, restricting the movement of the screw shaft 1 in the second direction X2. Therefore, the ball 3 does not pass through the first opening 17 and fall out.

[0070] Furthermore, the spiral ring 60 may be subjected to a load in the first direction X1 due to contact with the ball 3, and may move in the first direction X1. However, even if the spiral ring 60 moves in the first direction X1, it will come into contact with the first side surface 36, restricting its movement in the first direction X1. Therefore, the spiral ring 60 will not fall off the protrusion 30. Also, the amount of movement in the first direction due to the spiral ring 60 is only the amount of the minute gap M3 (see Figure 6). Therefore, the ball 3 will not fall out between the spiral ring 60 and the first end surface 15.

[0071] Next, a method for attaching the spiral ring 60 using the jig 200 will be described. Figure 8 is a cross-sectional view showing the process of attaching the spiral ring to the screw shaft of Embodiment 1. The jig 200 is frustoconical in shape. The jig 200 has a circular insertion surface 201, a circular contact surface 202 facing the opposite direction from the insertion surface 201 and having a larger diameter than the insertion surface 201, and an outer peripheral surface 203 that expands in diameter toward the second direction X2. A cylindrical projection 204 is formed in the center of the contact surface 202.

[0072] The jig 200 is used with its contact surface 202 in contact with the end face 32 of the screw shaft 1. The projection 204 is fitted into the center hole 33. Therefore, the jig 200 is positioned coaxially with the central axis 01 of the screw shaft 1. Furthermore, the diameter R201 of the insertion surface 201 is smaller than the inner diameter R60 (see Figure 5) of the spiral ring 60 at its natural length. Therefore, the insertion surface 201 of the jig 200 can be inserted into the inner circumference of the spiral ring 60 without expanding the diameter of the spiral ring 60. Also, the diameter of the contact surface 202 is the same as the outer diameter R30 of the projection 30. In this disclosure, the diameter of the contact surface 202 may be slightly larger than the outer diameter R30 of the projection 30, and is not limited to being the same as the outer diameter R30 of the projection 30.

[0073] As shown in Figure 8, the spiral ring 60 is installed by inserting the jig 200 into the inner circumference of the spiral ring 60 from the second direction X2. Next, the spiral ring 60 is moved along the outer surface 203 in the second direction X2 (see arrow A in Figure 8). As a result, the spiral ring 60 is pressed radially outward against the outer surface 203 and expands in diameter (see dashed line K1 in Figure 8).

[0074] Furthermore, when the spiral ring 60 is moved in the second direction X2, the component positioned on the inner circumference side of the spiral ring 60 switches from the jig 200 to the protrusion 30. In other words, the spiral ring 60 fits onto the outer circumference side of the protrusion 30 (see the dashed line K2 in Figure 8).

[0075] Furthermore, if the jig 200 is not positioned coaxially with the screw shaft 1, the spiral ring 60 will catch on the end face 32 of the protrusion 30 when the component positioned on the inner circumference of the spiral ring 60 switches from the jig 200 to the protrusion 30. In this embodiment, the jig 200 is positioned coaxially with the screw shaft 1. Therefore, the spiral ring 60 does not catch on the end face 32 of the protrusion 30.

[0076] Then, when the spiral ring 60 is moved in the second direction X2 along the outer circumferential surface 34 of the protrusion 30, the spiral ring 60 fits into the housing groove 35. After that, the jig 200 is removed from the screw shaft 1, and the installation method of the spiral ring 60 is completed.

[0077] As described above, according to the ball screw device 100 of Embodiment 1, the anti-loosening component 6 (spiral ring 60) can be attached to the screw shaft 1 after assembly of the ball screw device 100. Therefore, the structure is applicable to both sides of the screw shaft 1 in the axial direction.

[0078] Furthermore, in Embodiment 1, the spiral ring 60 fitted into the housing groove 35 is restricted from radial movement, axial movement, and rotation. As a result, the generation of contact noise between the spiral ring 60 and the inner surface of the housing groove 35 (first side surface 36, bottom surface 37, and second side surface 38 (first end surface 15)) is suppressed. Moreover, wear of the spiral ring 60 is also suppressed.

[0079] Although Embodiment 1 has been described above, this disclosure is not limited to the example described in Embodiment 1. For example, the diameter R37 of the bottom surface 37 in Embodiment 1 is larger than the inner diameter R60 of the spiral ring 60 at its natural length, but this disclosure is not limited to this. This disclosure may also describe a case where the diameter R37 of the bottom surface 37 is the same as the inner diameter R60 of the spiral ring 60 at its natural length. Alternatively, this disclosure may also describe a case where the diameter R37 of the bottom surface 37 is smaller than the inner diameter R60 of the spiral ring 60 at its natural length.

[0080] Furthermore, while the spiral ring 60 of Embodiment 1 has a wire length of 1.8 turns at its natural length, this disclosure is not limited to this. At its natural length, the wire 61 only needs to have at least one turn. As long as the wire 61 has at least one turn, the ball will not pass between one end and the other of the wire 61 and fall out. On the other hand, if the spiral ring 60 expands in diameter during fitting, as in Embodiment 1, even if the wire 61 has at least one turn at its natural length, the expansion may cause a gap to form between one end and the other of the wire 61. Therefore, the spiral ring 60 of this disclosure only needs to have at least one turn of wire 61 at both its natural length and when fitted.

[0081] Furthermore, while the spiral ring 60 of Embodiment 1 is tightly wound so that each part of the wire 61 has no gaps with other parts adjacent in the axial direction, the present disclosure may also be a spiral ring 60 formed by loose winding. In a spiral ring 60 formed by loose winding, each part of the wire 61 is spaced apart from other parts adjacent in the axial direction, creating axial gaps. Here, if the axial gap in the wire 61 is less than the diameter of the ball 3, it is prevented that the ball 3 will enter the axial gap in the wire 61 and fall off the outer raceway surface 12. Therefore, the present disclosure may be a spiral ring 60 formed by loose winding as long as the axial gap is less than the diameter of the ball 3.

[0082] Furthermore, in this embodiment, the axial size M1 of the accommodating groove 35 is larger than the axial size M2 of the spiral ring 60, but in this disclosure, the size M1 of the accommodating groove 35 and the size M2 of the spiral ring 60 may be the same.

[0083] Furthermore, in Embodiment 1, the spiral ring 60 is in contact with the first end face 15 (second side surface 38) when fitted, but in this disclosure, it may be in contact with the first side surface 36. Alternatively, the spiral ring 60 does not need to be in contact with both the first end face 15 (second side surface 38) and the first side surface 36 when fitted.

[0084] Furthermore, while the receiving groove 35 in the embodiment is located at the end of the outer circumferential surface of the protrusion 30 in the second direction X2, the receiving groove 35 in the present disclosure may be located in the first direction X1 rather than at the end of the outer circumferential surface of the protrusion 30 in the second direction X2. Also, while the first end face 15 constitutes the second side surface 38 in the embodiment, in the present disclosure, the first end face 15 and the second side surface 38 may be offset in the axial direction. Even with such modifications, as long as the distance between the spiral ring 60 and the first end face 15 is less than the diameter of the ball 3, the ball 3 will not fall out between the spiral ring 60 and the first end face 15.

[0085] Furthermore, in Embodiment 1, the outer diameter R61 of the spiral ring 60 when fitted (see Figure 6) is smaller than the outer diameter R10 of the screw shaft 1 (see Figure 1), but this disclosure is not limited to this. The outer diameter R61 of the spiral ring 60 when fitted only needs to be smaller than the inner diameter R2 of the nut 2 (see Figure 1). However, from the viewpoint of avoiding contact with the inner circumferential surface 20 of the nut 2 and the circulation part (in this embodiment, the ball 4), it is preferable that the outer diameter R61 of the spiral ring 60 when fitted is smaller than the BCD (Ball Center Diameter). The BCD is a circle connecting the centers O3 of the multiple balls 3 arranged in the raceway 7, and the diameter of that circle is R3 as shown in Figure 7. Moreover, the most preferred embodiment is when the outer diameter R61 of the spiral ring 60 when fitted is smaller than the outer diameter R10 of the screw shaft 1, as described in Embodiment 1.

[0086] On the other hand, the spiral ring 60 needs to be in contact with the ball 3 when mated. For this reason, the outer diameter R61 of the spiral ring 60 when mated needs to be larger than the diameter R3a (see Figure 7) of the circle formed by connecting the radially innermost portions 3a of the balls 3 arranged in the raceway 7. If the outer raceway surface 12 is a circular arc, portion 3a of the ball 3 will be in contact with the outer raceway surface 12. On the other hand, if the outer raceway surface 12 is a Gothic arc, the contact point 12a between the outer raceway surface 12 and the ball 3 will be radially outward from portion 3a of the ball 3. In addition, if the outer diameter R61 of the spiral ring 60 when mated is too small, the ball 3 may jump over the spiral ring 60 when it comes into contact with the spiral ring 60. Therefore, when the outer circumferential raceway surface 12 has a Gothic arc shape, it is preferable that the outer diameter R61 of the spiral ring 60 when fitted is larger than the diameter R12a (see Figure 7) of the circle formed by connecting the contact points 12a of the outer circumferential raceway surface 12 and the ball 3.

[0087] Furthermore, although the anti-loosening component 6 (spiral ring 60) of this disclosure is configured to be applicable to both sides in the axial direction of the screw shaft 1, it may also be applied to only one side in the axial direction of the screw shaft 1, as shown in Embodiment 1. Also, in the ball screw device 100 of Embodiment 1, if the screw shaft 1 moves in the first direction X1 relative to the nut 2, the ball 3 may fall out of the second opening 18. Therefore, the following modifications describe ball screw devices 100A and 100B that can prevent the ball 3 from falling out of the second opening 18. Note that the following modifications will focus on the differences from Embodiment 1.

[0088] (Variation 1) Figure 9 is a cross-sectional view of the ball screw device of Modification 1, cut in the axial direction. As shown in Figure 9, the screw shaft 1 of the ball screw device 100A of Modification 1 differs from Embodiment 1 in that a protruding portion (second protrusion) 30A is formed between the screw shaft body 10 and the connecting portion 31, protruding from the second end face 16. A housing groove 35A is formed in the protrusion 30A.

[0089] A spiral ring 160, which is a release prevention component (second release prevention component) 6A, is fitted into the housing groove 35A. The spiral ring 160 closes the second opening 18 from the second direction X2. Therefore, according to the modified example 1, when the amount of movement of the screw shaft 1 in the first direction X1 increases, the ball 3 (see Figure 7) comes into contact with the spiral ring 160. This prevents the ball 3 from passing through the second opening 18 and falling out.

[0090] (Modification 2) Figure 10 is a cross-sectional view of the ball screw device of Modification 2, cut in the axial direction. As shown in Figure 10, the screw shaft 1 of the ball screw device 100B of Modification 2 differs from Embodiment 1 in that a crimped portion 260 is formed near the end of the second direction X2 by crimping the screw threads. The crimped portion 260 reduces the groove width of the outer peripheral raceway surface 12, preventing the ball 3 from passing through. Therefore, in Modification 2 as well, when the amount of movement of the screw shaft 1 in the first direction X1 increases, the ball 3 (see Figure 7) comes into contact with the crimped portion 260. This prevents the ball 3 from passing through the second opening 18 and falling out.

[0091] The above describes Modification 1 and Modification 2. In Embodiment 1 and the above, the case in which the anti-loosening component 6 (spiral ring 60) is attached to the screw shaft 1 was described, but in this disclosure, the spiral ring 60 may be attached to the nut 2. Below, Modification 3 in which the spiral ring 60 is attached to the nut 2 will be described.

[0092] (Variation 3) Figure 11 is a cross-sectional view of the ball screw device of Modification 3, cut in the axial direction. As shown in Figure 11, the screw shaft 1 of the ball screw device 100C of Modification 3 differs from Embodiment 1 in that it does not have a protruding portion 30. The nut 2 of Modification 3 differs from Embodiment 1 in that it does not have a nut 4. The screw shaft body 10 of the screw shaft 1 of Modification 3 differs from Embodiment 1 in that a plurality of circulating groove surfaces 140 are formed on it. The nut 2 of Modification 3 differs from Embodiment 1 in that it has an annular portion 130 that protrudes from the end face (first end face 115) of the nut body 25. Furthermore, it differs from Embodiment 1 in that an anti-loosening component 6 (spiral ring 60) is attached to the inner circumference side of the annular portion 130. Details will be explained below.

[0093] The circulation groove surface 140 extends in a counter-helical direction opposite to the helical direction in which the outer circumferential raceway surface 12 extends, and connects both ends of the outer circumferential raceway surface 12. In Modification 3, the circulation groove surface 140 is formed by cutting the outer circumferential surface 11 of the screw shaft body 10. In Modification 3, the circulation part is given as an example of a circulation groove surface 140 formed by cutting the outer circumferential surface 11 of the screw shaft body 10, but this disclosure is not limited to this. For example, this disclosure may use a spindle in which the circulation groove surface 140 is formed on the radially outer surface, and there are no particular restrictions on the type of circulation part.

[0094] Figure 12 is an enlarged view of the nut and spiral ring of the modified example 3. As shown in Figure 12, the nut body 25 has a first end face 115 facing a first direction X1 and a second end face 116 (see Figure 11) facing a second direction X2. The first end face 115 has a first opening 117 which is cut out in the circumferential direction. The first opening 117 opens the inner circumferential raceway surface 21 in the first direction X1. The second end face 116 also has a second opening 118 (see Figure 11) which opens the inner circumferential raceway surface 21 in the second direction X2.

[0095] The annular portion 130 protrudes from the first end face 115 in the first direction X1. The annular portion 130 is formed in an annular shape around the central axis O1. The inner diameter of the annular portion 130 is R130. This inner diameter R130 of the annular portion 130 is larger than the inner diameter R2 of the nut body 25 (see Figure 1). Furthermore, the inner diameter R130 of the annular portion 130 is larger than the diameter R21a of the groove bottom 21a of the inner circumferential raceway surface 21. The groove bottom 21a of the inner circumferential raceway surface 21 is located in the center of the width direction of the inner circumferential raceway surface 21 and is the part of the inner circumferential raceway surface 21 that is recessed radially to the outermost side.

[0096] An annular receiving groove 135 is formed on the inner circumferential surface 131 of the annular portion 130, recessing radially outward. The inner surface of the receiving groove 135 has a first side surface 136 positioned in a first direction X1 relative to the receiving groove 135, a bottom surface 137, and a second side surface 138 positioned in a second direction X2 relative to the receiving groove 135. The receiving groove 135 is located at the end of the inner circumferential surface 131 of the annular portion 130 in the second direction X2. Therefore, the second side surface 138 is formed by the first end surface 115.

[0097] In modified example 3, the spiral ring 60 is housed in the housing groove 135 of the annular portion 130. The spiral ring 60 closes the first opening 117 from the first direction X1. Also, the outer diameter R160 of the spiral ring 60 at its natural length (see Figure 5) is larger than the inner diameter R130 of the annular portion 130. Therefore, when attaching the spiral ring 60 to the nut 2, the spiral ring 60 is first elastically deformed to reduce its diameter, and then inserted into the annular portion 130. Next, the force applied to the spiral ring 60 is removed, and the spiral ring 60 expands in diameter. Finally, the spiral ring 60 is fitted into the housing groove 135. Note that in this disclosure, a jig may be used when attaching the spiral ring 60 to the nut 2.

[0098] Furthermore, the axial size of the receiving groove 35 is slightly larger than the axial size of the spiral ring 60. Therefore, it is easier to fit the spiral ring 60 into the receiving groove 135 than if the axial sizes of the receiving groove 135 and the spiral ring 60 were the same.

[0099] The diameter R137 of the bottom surface 137 of the housing groove 135 is smaller than the outer diameter R160 of the spiral ring 60 at its natural length (see Figure 5). Therefore, the outer diameter of the spiral ring 60 when fitted is smaller than at its natural length. In other words, the outer circumference of the spiral ring 60 is in contact with the bottom surface 37 of the housing groove 35 without any gaps. As a result, radial movement of the spiral ring 60 is suppressed. In addition, a restoring force (a force that tries to expand) acts on the spiral ring 60 to return to its original shape, resulting in a large frictional force with the bottom surface 137. As a result, axial movement and rotation of the spiral ring 60 are suppressed. From the above, the generation of contact noise between the spiral ring 60 and the inner surface of the housing groove 135 (first side surface 136, bottom surface 137, and second side surface 138 (first end surface 115)) is suppressed. Furthermore, wear of the spiral ring 60 is also suppressed.

[0100] Furthermore, the inner diameter R161 of the spiral ring 60 when fitted is larger than the inner diameter R2 of the nut body 25 (see Figure 1). Therefore, the spiral ring 60 does not protrude radially inward from the inner circumferential surface 20 of the nut body 25. Thus, contact between the spiral ring 60 and the outer circumferential surface 11 of the screw shaft 1 is avoided.

[0101] Figure 13 is a cross-sectional view of the ball screw device of Modification 3 (with the nut moved in the second direction) cut in the axial direction. Next, the case in which the nut 2 moves in the second direction X2 relative to the screw shaft 1 will be explained. As shown in Figure 13, when the amount of movement of the nut 2 in the second direction X2 becomes large and the ball 3 on the first track 7a attempts to pass through the first opening 117, the ball 3 comes into contact with the spiral ring 60. Therefore, the spiral ring 60 catches on the ball 3, preventing the nut 2 from moving further in the second direction X2. Thus, the ball 3 does not pass through the first opening 117 and fall out. In addition, the spiral ring 60 receives a load in the first direction X1 due to contact with the ball 3, but the spiral ring 60 comes into contact with the first side surface 136, restricting its movement in the first direction X1. Therefore, the spiral ring 60 does not fall off the annular portion 130 (nut 2).

[0102] Although Modification 3 has been described above, this disclosure is not limited to the example shown in Modification 3, with respect to the case where the spiral ring 60 is attached to the nut 2. For example, the diameter R137 of the bottom surface 137 may be the same as the outer diameter R160 of the spiral ring 60 at its natural length, or it may be larger than the outer diameter R160 of the spiral ring 60 at its natural length.

[0103] Furthermore, in the case where the spiral ring 60 is attached to the nut 2, the inner diameter R161 of the spiral ring 60 when fitted may be greater than or equal to the diameter R3a (see Figure 7) of the circle connecting the centers O3 of the multiple balls 3 arranged in the raceway 7. With such a configuration, the spiral ring 60 is less likely to come into contact with the outer circumferential surface 11 of the screw shaft 1.

[0104] Furthermore, when the spiral ring 60 is attached to the nut 2, the spiral ring 60 needs to be in contact with the ball 3 during mating. That is, as shown in Figure 13, the inner diameter R161 of the spiral ring 60 during mating needs to be smaller than the diameter R103a of the circle formed by connecting the radially outermost portions 103a of the balls 3 arranged in the raceway 7. Note that if the inner raceway surface 21 is a circular arc, portion 103a of the ball 3 will be in contact with the inner raceway surface 21. If the inner raceway surface 21 is a Gothic arc shape, the contact point 21b between the inner raceway surface 21 and the ball 3 will be radially inward from portion 103a of the ball 3 (see Figure 13).

[0105] Furthermore, when the spiral ring 60 is attached to the nut 2, if the inner diameter R161 of the spiral ring 60 during fitting is too large, there is a possibility that the ball 3 may jump over the spiral ring 60 when it comes into contact with the spiral ring 60. For this reason, when the inner circumferential raceway surface 21 has a Gothic arc shape, it is preferable that the outer diameter of the spiral ring 60 during fitting is smaller than the diameter R21b of the circle formed by connecting the contact points 21b of the inner circumferential raceway surface 21 and the ball 3 (see Figure 13).

[0106] Furthermore, although the anti-loosening component 6 (spiral ring 60) of this disclosure is configured to be applicable to both sides of the nut 2 in the axial direction, it may also be applied to only one side of the screw shaft 1 in the axial direction, as shown in Modification 3.

[0107] Furthermore, although not specifically shown in the figures, the present disclosure may also be a ball screw device in which the spiral ring 60 is attached to both sides of the nut 2. That is, the annular portion 130 of the ball screw device of the present disclosure has a first annular portion that protrudes from one end face (first end face 115) of the nut body 25 and a second annular portion that protrudes from the other end face (second end face 116) of the nut body 25. The anti-loosening component 6 (spiral ring 60) may have a first anti-loosening component that fits into the housing groove of the first annular portion and a second anti-loosening component that fits into the housing groove of the second annular portion.

[0108] Furthermore, although not specifically shown in the figures, in this disclosure, the spiral ring 60 may be attached to only one axial side of the nut 2, and a crimped portion may be formed on the other axial side of the nut 2. In other words, the annular portion 130 of the ball screw device of this disclosure has a first annular portion that protrudes from one end face (first end face 115) of the nut body 25. The anti-loosening component 6 (spiral ring 60) has a first anti-loosening component that fits into a housing groove of the first annular portion. A crimped portion is formed at the other axial end of the nut body 25, where the screw threads are crimped. A portion of the inner circumferential raceway surface 21 may have a reduced groove width due to the crimped portion.

[0109] Furthermore, in Modification 3, the accommodating groove 135 is located at the end of the inner circumferential surface 131 of the annular portion 130 in the second direction X2, but in this disclosure, the accommodating groove 135 may be located in the first direction X1 rather than at the end of the outer circumferential surface of the annular portion 130 in the second direction X2. Also, in Modification 3, the first end face 115 constitutes the second side surface 138, but in this disclosure, the first end face 115 and the second side surface 138 may be offset from each other in the axial direction.

[0110] The ball screw device in which the spiral ring 60 is attached to the nut 2 has been described above, but configurations other than those described above, as described in Embodiment 1, Modification 1 and Modification 2, may also be applied.

[0111] Furthermore, this disclosure may also be a combination of the following configurations. (1) A screw shaft having an outer raceway surface formed on its outer surface, A nut in which the screw shaft is inserted into the inner circumference and an inner circumference raceway surface is formed on the inner circumference, A plurality of balls arranged in a track between the outer circumferential track surface and the inner circumferential track surface, An annular anti-loosening component, viewed from an axial direction parallel to the central axis of the aforementioned screw shaft, Equipped with, One of the screw shaft and the nut has a circulation section, The other of the screw shaft and the nut is An opening that causes the outer circumferential raceway surface or the inner circumferential raceway surface to open in the axial direction, An annular receiving groove recessed radially from the outer circumferential surface of the screw shaft or the inner circumferential surface of the nut, It has, The aforementioned anti-bulging component is a spiral ring that can expand and contract in diameter through elastic deformation. The spiral ring is fitted into the housing groove and closes the opening from the axial direction. Ball screw device. (2) The nut has the circulation part, The aforementioned screw shaft is The screw shaft body having the aforementioned outer circumferential raceway surface, A protruding portion that extends from the end face of the screw shaft body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the outer circumferential raceway surface is opened in the axial direction. The outer circumferential surface of the protrusion is formed with the receiving groove which is recessed radially inward. The inner diameter of the spiral ring at its natural length is smaller than the outer diameter of the protrusion. The spiral ring has an inner diameter larger than the outer diameter of the protrusion and is capable of elastic deformation. (1) The ball screw device described above. (3) A screw shaft having an outer raceway surface formed on its outer surface, A nut in which the screw shaft is inserted into the inner circumference and an inner circumference raceway surface is formed on the inner circumference, A plurality of balls arranged in a track between the outer circumferential track surface and the inner circumferential track surface, An annular anti-loosening component, viewed from an axial direction parallel to the central axis of the aforementioned screw shaft, Equipped with, One of the screw shaft and the nut has a circulation section, The other of the screw shaft and the nut is An opening that causes the outer circumferential raceway surface or the inner circumferential raceway surface to open in the axial direction, An annular receiving groove recessed radially from the outer circumferential surface of the screw shaft or the inner circumferential surface of the nut, It has, The aforementioned anti-bulging component is a spiral ring that can expand and contract in diameter through elastic deformation. The spiral ring is fitted into the housing groove and closes the opening from the axial direction. The nut has the circulation part, The aforementioned screw shaft is The screw shaft body having the aforementioned outer circumferential raceway surface, A protruding portion that extends from the end face of the screw shaft body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the outer circumferential raceway surface is opened in the axial direction. The outer circumferential surface of the protrusion is formed with the receiving groove which is recessed radially inward. The inner diameter of the spiral ring at its natural length is smaller than the outer diameter of the protrusion. The spiral ring has an inner diameter larger than the outer diameter of the protrusion and is capable of elastic deformation. Ball screw device. (4) The diameter of the bottom surface of the aforementioned groove is larger than the inner diameter of the spiral ring at its natural length. (2) or (3) the ball screw device described above. (5) The outer diameter of the spiral ring attached to the aforementioned groove is less than or equal to the diameter of the circle formed by connecting the centers of the plurality of balls arranged in the aforementioned track. A ball screw device as described in any one of (2) to (4). (6) The outer diameter of the spiral ring attached to the aforementioned groove is less than or equal to the outer diameter of the screw shaft body. A ball screw device as described in any one of (2) to (4). (7) The outer perimeter track surface has a Gothic arc shape. The outer diameter of the spiral ring fitted into the aforementioned groove is greater than the diameter of the circle formed by connecting the contact points between the outer circumferential raceway surface and the ball. A ball screw device as described in any one of (2) to (4). (8) The outer diameter of the protrusion is less than or equal to the diameter of the groove bottom on the outer circumferential raceway surface. A ball screw device as described in any one of (2) to (7). (9) A center hole is formed in the center of the end face of the aforementioned protruding portion. A ball screw device as described in any one of (2) to (8). (10) The aforementioned protrusion is A first protrusion that protrudes from one end face of the screw shaft body, A second projection protruding from the other end face of the screw shaft body, It has, The aforementioned anti-detection component is, A first anti-loosening component that fits into the housing groove of the first protrusion, A second anti-loosening component that fits into the housing groove of the second protrusion, It has A ball screw device as described in any one of (2) to (9). (11) The aforementioned projection has a first projection that protrudes from one end face of the screw shaft body, The aforementioned anti-loosening component has a first anti-loosening component that fits into the housing groove of the first protrusion, A crimped portion is formed at the other end of the screw shaft body in the axial direction, where a screw thread is crimped. The groove width of a portion of the outer circumferential raceway surface is reduced by the crimping portion. A ball screw device as described in any one of (2) to (9). (12) The screw shaft has the circulation part, The aforementioned nut is The annular nut body having the aforementioned inner circumferential raceway surface, An annular portion protruding from the end face of the nut body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the inner circumferential raceway surface is opened in the axial direction. The inner circumferential surface of the annular portion has the receiving groove formed in which the groove is recessed radially outward. The outer diameter of the spiral ring at its natural length is greater than the inner diameter of the annular portion. The spiral ring has an outer diameter smaller than the inner diameter of the annular portion and is capable of elastic deformation. (1) The ball screw device described above. (13) A screw shaft having an outer raceway surface formed on its outer surface, A nut in which the screw shaft is inserted into the inner circumference and an inner circumference raceway surface is formed on the inner circumference, A plurality of balls arranged in a track between the outer circumferential track surface and the inner circumferential track surface, An annular anti-loosening component, viewed from an axial direction parallel to the central axis of the aforementioned screw shaft, Equipped with, One of the screw shaft and the nut has a circulation section, The other of the screw shaft and the nut is An opening that causes the outer circumferential raceway surface or the inner circumferential raceway surface to open in the axial direction, An annular receiving groove recessed radially from the outer circumferential surface of the screw shaft or the inner circumferential surface of the nut, It has, The aforementioned anti-bulging component is a spiral ring that can expand and contract in diameter through elastic deformation. The spiral ring is fitted into the housing groove and closes the opening from the axial direction. The screw shaft has the circulation part, The aforementioned nut is The annular nut body having the aforementioned inner circumferential raceway surface, An annular portion protruding from the end face of the nut body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the outer circumferential raceway surface is opened in the axial direction. The inner circumferential surface of the annular portion has the receiving groove formed in which the groove is recessed radially outward. The outer diameter of the spiral ring at its natural length is greater than the inner diameter of the annular portion. The spiral ring has an outer diameter smaller than the inner diameter of the annular portion and is capable of elastic deformation. Ball screw device. (14) The diameter of the bottom surface of the aforementioned groove is smaller than the outer diameter of the spiral ring at its natural length. (12) or (13) the ball screw device described above. (15) The inner diameter of the spiral ring attached to the aforementioned groove is greater than or equal to the diameter of the circle formed by connecting the centers of the multiple balls arranged in the aforementioned track. A ball screw device as described in any one of (12) to (14). (16) The inner diameter of the spiral ring attached to the aforementioned groove is greater than or equal to the inner diameter of the nut body. A ball screw device as described in any one of (12) to (14). (17) The inner circumferential track surface has a Gothic arc shape. The inner diameter of the spiral ring fitted into the aforementioned groove is smaller than the diameter of the circle formed by connecting the contact points between the inner circumferential raceway surface and the ball. A ball screw device as described in any one of (12) to (14). (18) The aforementioned annular portion is, A first annular portion protruding from one end face of the nut body, A second annular portion protruding from the other end face of the nut body, It has, The aforementioned anti-detection component is, A first anti-loosening component that fits into the housing groove of the first annular portion, A second anti-loosening component that fits into the housing groove of the second annular portion, It has A ball screw device as described in any one of (12) to (17). (19) The annular portion has a first annular portion that protrudes from one end face of the nut body, The aforementioned anti-loosening component has a first anti-loosening component that fits into the housing groove of the first annular portion, A crimped portion is formed at the other axial end of the nut body, where a screw thread is crimped. A portion of the inner circumferential raceway surface has a reduced groove width due to the crimping portion. A ball screw device as described in any one of (12) to (17). [Explanation of symbols]

[0112] 1 Screw shaft 2 nuts 3 balls 4 panels 5 sleeves 6, 6A Anti-bullet parts 7 orbit 10 Screw shaft body 11 Outer surface 12 Outer raceway surface 13 Groove bottom 15 First end surface 16 Second end face 17. First opening (opening) 18. Second opening (opening) 20 Inner surface 21 Inner raceway surface 22 Through hole 30, 30A protrusion 31 Connecting part 32 End face 33 Center Hole 35, 35A, 135 storage grooves 36, 136 1st side 37, 137 base 38, 138 second aspect 40, 140 Circulation groove surface 60, 160 spiral rings 61 Wire rod 62 one end 63 Other end 64 Middle section 100, 100A, 100B, 100C Ball Screw Device 115 1st end face 116 Second end face 117 First opening (opening) 118 Second opening (opening) 130 Ring section 200 jigs 201 Insertion surface 202 Contact surface 204 Protrusion 260 Crimping section

Claims

1. A screw shaft having an outer raceway surface formed on its outer surface, A nut in which the screw shaft is inserted into the inner circumference and an inner circumference raceway surface is formed on the inner circumference, A plurality of balls arranged in a track between the outer circumferential track surface and the inner circumferential track surface, An annular anti-loosening component, viewed from an axial direction parallel to the central axis of the aforementioned screw shaft, Equipped with, One of the screw shaft and the nut has a circulation section, The other of the screw shaft and the nut is An opening that causes the outer circumferential raceway surface or the inner circumferential raceway surface to open in the axial direction, An annular receiving groove recessed radially from the outer circumferential surface of the screw shaft or the inner circumferential surface of the nut, It has, The aforementioned anti-bulging component is a spiral ring that can expand and contract in diameter through elastic deformation. The spiral ring is fitted into the housing groove and closes the opening from the axial direction. Ball screw device.

2. The nut has the circulation part, The aforementioned screw shaft is The screw shaft body having the aforementioned outer circumferential raceway surface, A protruding portion that extends from the end face of the screw shaft body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the outer circumferential raceway surface is opened in the axial direction. The outer circumferential surface of the protrusion is formed with the receiving groove which is recessed radially inward. The inner diameter of the spiral ring at its natural length is smaller than the outer diameter of the protrusion. The spiral ring has an inner diameter larger than the outer diameter of the protrusion and is capable of elastic deformation. The ball screw device according to claim 1.

3. The diameter of the bottom surface of the aforementioned groove is larger than the inner diameter of the spiral ring at its natural length. The ball screw device according to claim 2.

4. The outer diameter of the spiral ring attached to the aforementioned groove is less than or equal to the diameter of the circle formed by connecting the centers of the plurality of balls arranged in the aforementioned track. The ball screw device according to claim 2.

5. The outer diameter of the spiral ring attached to the aforementioned groove is less than or equal to the outer diameter of the screw shaft body. The ball screw device according to claim 2.

6. The outer perimeter track surface has a Gothic arc shape. The outer diameter of the spiral ring fitted into the aforementioned groove is greater than the diameter of the circle formed by connecting the contact points between the outer circumferential raceway surface and the ball. The ball screw device according to claim 2.

7. The outer diameter of the protrusion is less than or equal to the diameter of the groove bottom on the outer circumferential raceway surface. The ball screw device according to claim 2.

8. A center hole is formed in the center of the end face of the aforementioned protruding portion. The ball screw device according to claim 2.

9. The aforementioned protrusion is A first protrusion that protrudes from one end face of the screw shaft body, A second projection protruding from the other end face of the screw shaft body, It has, The aforementioned anti-detection component is, A first anti-loosening component that fits into the housing groove of the first protrusion, A second anti-loosening component that fits into the housing groove of the second protrusion, It has A ball screw device according to any one of claims 2 to 8.

10. The aforementioned projection has a first projection that protrudes from one end face of the screw shaft body, The aforementioned anti-loosening component has a first anti-loosening component that fits into the housing groove of the first protrusion, A crimped portion is formed at the other end of the screw shaft body in the axial direction, where a screw thread is crimped. The groove width of a portion of the outer circumferential raceway surface is reduced by the crimping portion. A ball screw device according to any one of claims 2 to 8.

11. The screw shaft has the circulation part, The aforementioned nut is The annular nut body having the aforementioned inner circumferential raceway surface, An annular portion protruding from the end face of the nut body, It has, The end face has an opening formed in which a part of the circumferential direction is cut out, and the inner circumferential raceway surface is opened in the axial direction. The inner circumferential surface of the annular portion has the receiving groove formed in which the groove is recessed radially outward. The outer diameter of the spiral ring at its natural length is greater than the inner diameter of the annular portion. The spiral ring has an outer diameter smaller than the inner diameter of the annular portion and is capable of elastic deformation. The ball screw device according to claim 1.

12. The diameter of the bottom surface of the aforementioned groove is smaller than the outer diameter of the spiral ring at its natural length. The ball screw device according to claim 11.

13. The inner diameter of the spiral ring attached to the aforementioned groove is greater than or equal to the diameter of the circle formed by connecting the centers of the multiple balls arranged in the aforementioned track. The ball screw device according to claim 11.

14. The inner diameter of the spiral ring attached to the aforementioned groove is greater than or equal to the inner diameter of the nut body. The ball screw device according to claim 11.

15. The inner circumferential track surface has a Gothic arc shape. The inner diameter of the spiral ring fitted into the aforementioned groove is smaller than the diameter of the circle formed by connecting the contact points between the inner circumferential raceway surface and the ball. The ball screw device according to claim 11.

16. The aforementioned annular portion is, A first annular portion protruding from one end face of the nut body, A second annular portion protruding from the other end face of the nut body, It has, The aforementioned anti-detection component is, A first anti-loosening component that fits into the housing groove of the first annular portion, A second anti-loosening component that fits into the housing groove of the second annular portion, It has A ball screw device according to any one of claims 11 to 15.

17. The annular portion has a first annular portion that protrudes from one end face of the nut body, The aforementioned anti-loosening component has a first anti-loosening component that fits into the housing groove of the first annular portion, A crimped portion is formed at the other axial end of the nut body, where a screw thread is crimped. A portion of the inner circumferential raceway surface has a reduced groove width due to the crimping portion. A ball screw device according to any one of claims 11 to 15.

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